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Über dieses Buch

Progress in Pacific Polymer Science 3 continues the record of the current status of major topics in polymer science.
The invited lecturers cover the following topics:
- Adding Value to Natural Polymers
- Polymers and the Environment
- Polymers in Mining and Mineral Processing
- Multicomponent Polymer Systems
- Characterization, Properties and Processing
- Functional Polymers
- Polymers for Medical Applications
- Polymer Recycling
- Polymer Surfaces of Biological Significance
- New and Advanced Polymer Materials

Inhaltsverzeichnis

Frontmatter

Kinetics of Phase Separation of Polymer Blends

The phase diagram, especially coexistence curve, can provide us an indispensable information in studying the phase separation kinetics since it gives the stability and the fractional phase volume of the system that are most important factors controlling the phase separation processes. In spite of its importance, there are a very few studies because of experimental difficulties. In this study, we have overcome the difficulties and determined precise coexistence curves of polymer blends.[1–4] Taking advantage of the established coexistence curves, we have studies kinetics of early and late stages of phase separation. As to the early stage, time-evolution of concentration fluctuations in the metastable region has been studied using time-resolved synchrotron small-angle x-ray scattering.[5] For the late stage, the crossover from co-continuous to droplet structure has been investigated, which is primarily governed by the fractional phase volume.[6] Furthermore, using the information obtained here, the morphological structure induced by two-step temperature jump has also been investigated.[7–9] Through these studies, we will demonstrate importance of the coexistence curve in studying phase-separation kinetics.

Takuhei Nose

Cell Adhesion and Protein Adsorption on Gradient Surfaces

A new method for preparing a wettability gradient on polymer surfaces was developed. Low density polyethylene sheets were treated in air with corona from a knife-type electrode whose power gradually increases along the sample length. The polymer surfaces oxidized gradually with the increasing power and the wettability gradient was created on the surfaces as evidenced by the measurement of water contact angles, Fourier-transform infrared spectroscopy in the attenuated total reflectance mode, and electron spectroscopy for chemical analysis. The wettability gradient surfaces prepared were used to investigate the interactions of model protein and cells in terms of the surface hydrophilicity/hydrophobicity of polymeric materials.

Hai Bang Lee, Jin Ho Lee

Rheological Properties of Blends: Facts and Challenges

Three forces will continue to provide incentive for the industry to produce new polymer blends: the ability to tailor product properties to a particular performance cost balance; fast entry into new markets; and it is easier to develop products for small or niche markets than by synthesizing new polymers. The utilization of polymer blends in commerce represents some 16% of all plastics and the sector is growing at a rate of approximately 10% per year. We expect that polymer blends will grow at a much faster pace in the next decade. The most important class of blends from the commercial viewpoint are the so-called immiscible blends, where the presence of a distinct minor phase may be observed. The minor phase in an immiscible polymer blend is deformable and a wide range of sizes and shapes can thus be obtained for this dispersed phase during processing [1]. Both the size and the shape of the minor phase can influence a multiplicity of physical properties. At present the processing/ morphology/ property relationships in immiscible and partly miscible blends remain poorly understood and a given processing strategy may result in high value added blends. Rheological methods are powerful tools to elucidate such relationships. The morphology of blends is strongly dependent on the rheological properties of the components and rheological properties are needed to understand the processing of blends and changes occurring during processing. Conversely, the blends’ morphology affects the rheological properties.

P. J. Carreau, M. Bousmina, A. Ajji

Hydroboration Polymerization

This paper describes “Hydroboration Polymerization” as a novel methodology for the preparation of organoboron polymers. A polyaddition between diene and thexylborane produced a polymer consisting of C-B bonds in the main chain. The resulting organoboron polymers can be regarded as a polymer homologue of trialkylborane and can be expected as a novel type of reactive polymers. On the other hand, hydroboration polymerization of diene with monobromoborane produced poly(organoboron halide)s as a polymeric Lewis acid. Furthermore, hydroboration polymerization of dicyano compounds such as isophthalonitrile with t-butylborane produced an air-stable boroncontaining polymer (polycyclodiborazane) having B-N four-membered rings via dimerization of iminoborane species.

Yoshiki Chujo

Stereospecific Polymerization of Styrene

Homogeneous titanium compound and methyialuminoxane (MAO) system is an effective catalyst for syndiospecific polymerization of styrene. The molecular weight distribution (MWD) is narrow (MWD⇋2). A wide MWD can be obtained by using two kinds of titanium compound and MAO catalyst. Heterogeneous titanium compound containing halogen makes a mixture of isotactic and syndiotactic components. The ratio is dependent on the molar ratio of A1 to Ti. The result of ESR measurement suggests that Ti(3+) species are important as a highly active site for producing syndiotactic polystyrene (SPS).

M. Kuramoto

Polymer Design for Minimally Adhesive Surfaces

In connection with our interest in the development of minimally adhesive surfaces to discourage the settlement of marine organisms, we have investigated polyurethanes and polyureas containing polydimethylsiloxane (PDMS) segments. A two-step polymerization method was used to prepare dimethylsiloxane-urea-urethane copolymers with 1,4-benzenedimethanol as the chain extender. Thermal and mechanical properties of copolymers with chain extenders were found to be superior to those without chain extender, due to the additional hydrogen bonding interactions for the former. Surface composition was determined by angle-dependent electron spectroscopy for chemical analysis (ESCA). Effects of segmental length and annealing on the surface composition were investigated. One of the siloxane containing copolymers was used as the minor component (1.6, 2.5 and 6.0 wt %) in a series of blends with a poly(ether-urethane), which preserved the mechanical properties of the poly(ether-urethane) as well as the surface properties of the poly(siloxane-urea-urethane).

K. J. Wynne, T. Ho, R. A. Nissan, X. Chen, J. A. Gardella

Some Recent Developments in the Aminoxyl Radical Trapping Technique

The radical trapping technique employing the stable aminoxyl (nitroxide) 1 as a radical scavenger, has been used to study (a) the initiation stage in the mechanism of formation of alternating copolymers (b) the reaction of diphenylphosphinoyl and dimethyl phosphoryl radicals with monomers (c) the unusual polymerisation characteristics of maleates and fumarates.

S. E. Bottle, W. K. Busfield, I. D. Grice, K. Heiland, I. D. Jenkins, W. Meutermans, M. Monteiro

The Surface Excess Structure in 1,4-Polyisoprene-Polyacetylene Copolymer Solutions

Copolymers of 1,4-polyisoprene-polyacetylene with up to 25% polyacetylene are soluble in organic solvents and, like native polyacetylene, have interesting electrical and non linear optical properties. Because the molecules are amphiphilic techniques analogous to Langmuir-Blodgett methods may prove useful for self assembly and so here we study the surface excess of toluene solutions by the specular reflection of neutrons. A surface layer structure with excess PA at the air/solvent interface is characterised using the isotopic replacement method in neutron scattering.

J. W. White, J. C. H. Kerr, J. Penfold, P. M. Saville, R. K. Thomas

Helix-Sense-Selective Polymerization of Methacrylate and Conformational Characteristics of the Polymers

We have been studying the helix-sense-selective polymerization of bulky methacrylates such as triphenylmethyl methacrylate (TrMA),1 diphenyl-2-pyridylmethyl methacrylate (D2PyMA),2 phenyl-2-pyridyl-o- and m-tolyImethyl methacrylates (PPyoTMA and PPymTMA),3,4 and (S)-(-)-diphenyl(1-methylpyrrolidin-2-yl)methyl methacrylate (DMPMA)5 with chiral anionic initiators. In these polymerizations, optically active polymers with one-handed helical structure have been obtained and some of the polymers exhibited characteristic conformational transition in solution.6 In the present paper, we describe helix-sense-selective polymerization of 1-phenyldibenzosuberyl methacrylate (PDBSMA), diphenyl-3-pyridylmethyl methacrylate (D3PyMA) and phenyl[bis(2-pyridyl)]methyl methacrylate (PB2PyMA) by means of chiral anionic initiators and conformational transition of the obtained polymers. Asymmetric radical polymerization of PDBSMA is also reported because this monomer can also afford a helical, highly isotactic polymer by radical mechanism.

Yoshio Okamoto, Tamaki Nakano

Spectroscopic Studies of Conducting Polymers on Oxide Catalysts

A variety of spectroscopic techniques have been utilised to study the polymerisation of monomers such as acetylene or pyrrole within zeolite channels. The nature of the cations located in the zeolite framework was demonstrated to be a significant factor in the design of a successful catalyst. In particular cesium ions enhanced the degree of acetylene polymerisation relative to the situation with sodium, and copper ions were active for the polymerisation of pyrrole. Other factors such as the presence of Lewis acid sites and the coverage of adsorption sites by acetylene were also determined to be important in the mechanism for acetylene polymerisation. Resonance Raman studies indicated that polypyrrole formed within a zeolite channel was partially charged i.e. in the conducting state. Furthermore, this charge was associated with quinoid structures in the polymer chains. X-ray photoelectron spectroscopy (XPS) and photoacoustic infrared spectroscopy (PAIRS) data also provided evidence for the presence of a charged polymer segment. UV/VIS analysis allowed a detailed band description of the conducting polymer to be assimilated, and the level of doping to be estimated. ESR investigations further demonstrated formation of polaron charge carriers at the expense of Cu2+.

G. J. Millar, G. F. McCann, G. A. Bowmaker, R. P. Cooney

Synthesis of Poly (p-Epoxystyrene-co-N-Phenylmaleimide-co-styrene)

The photosensitive negative resists containing p-epoxystyrene were synthesized. The synthesis was performed starting from chloromethylation of 2-phenylethyl bromide, then dehydrobromi nation and copolymerization with N-phenylmaleimide and styrene to yield p-chloromethylstyrene-N-phenylmaleimide-styrene copolymer. The comparison of glass transition temperature of these copolymers and with poly(p-chloromethylstyrene-co-styrene) exhibited that the existing N-phenylmaleimide moiety in the polymer chain affected on the glass transition temperature. The more N-phenylmaleimide moiety was in the polymer chain, the higher the glass transition temperature was. The conversion of the chloromethyl group to the carboxaldehyde group and then to the epoxide group were consequently carried out. Accordingly, poly(p- epoxystyrene-co-N-phenylmaleimide-co-styrene) could be synthesized. However, by using this synthetic route, the chloromethyl and carboxaldehyde groups would be retained partially in the copolymer.

B. Pulpoka, P. C. Ternai, F. Schue, S. Tantayanon

Production, Modifications and Applications of Chitosan in Vietnam

Chitin is a cellulose-like biopolymer distributed widely in nature. Chitosan is the deacetylated product of chitin. The chemical structure of chitin and chitosan can be seen to be very similar to that of cellulose, the difference being that OH group of each glucose unit in cellulose is substituted by an acetylated amino group (-NHCOCH3) in chitin and an amino group (-NH2) in chitosan.

Dang Van Luyen

A Novel Polymer Film that Controls Light Transmission

This polymer film is a novel light control film which scatters only incident lights from particular angles and transmits incident lights from all other angles. This unique light control function is caused by the microstructure in the polymer film.The optical properties described in this paper support that the principle of an angle dependent light control function can be explained mainly by diffraction due to the microstructure like a stack of various transmission volume phase gratings. The proposed mechanism of forming the unique microstructure during photopolymerization is due to the diffraction of exposure lights by the polymerization-induced microgels.

M. Honda, S. Hozumi, S. Kitayama

The γ-Initiated Degradation of Polypropylene: Stabilization by Phenols

The effects of various phenols and some hindered amines have been compared both during the γ-irradiation process and during the post-irradiation oxidations of polypropylene films and test strips. Oxidation product formation, yellowing and embrittlement (as measured in an instrumented bend test) have been compared with product formation. A partial correlation between suppression of oxidation during the irradiation step with long term, post-irraidation oven aging at 60°C was found, but complicated by extensive destruction during irradiation of the active phenolic functionality in some additives, essential for peroxyl radical scavenging. Very long lifetimes with barely detectable yellowing were found for combinations of the amines with completely unhindered or only partially hindered phenols.

D. J. Carlsson, S. Falicki, J. M. Cooke, D. J. Gosciniak

Construction of Polypeptide Tertiary Structure by the Template-Assisted Synthesis

Two helical chains of dodecapeptides were connected to a cyclic octapeptide in a parallel (F12-C8KL) or an antiparallel orientation (CH2). CD measurements revealed that two dodecapeptide chains took α-helical conformation and were non-aggregative in organic solvents, but assembled intramolecularly in a buffer solution. The formation of the supersecondary structure was also indicated by fluorescent probes introduced to the chain- end region. Since each peptide chain was designed to take an amphiphilic α-helical structure, the hydrophobic surfaces face each other in the α-helix assembly. The intramolecular assembly caused a distortion of peptide chains from α-helical conformation in a buffer solution. The distortion of CH2 was less marked than that of F12-C8KL. CH2 was bound by λ DNA, while CHI, which is a single-chain analog of CH2, and F12-C8KL, which is analoguous to CH2 without a terminal anthryl group, were not. It is considered that CH2 binds itself to DNA backbone through electrostatic interaction of two Lys residues in one chain, and that the anthryl group of the other chain is intercalated into a base pair. The mechanism of CH2/DNA interaction changed by the addition of Ca2+ probably due to Ca2+ complexation with the cyclic moiety of CH2.

Yukio Imanishi, Shunsaku Kimura, Tatsuro Tsuchimoto

A New Family of Water-Soluble Polymers: Polymers of N-Substituted Acrylamide Derivatives

Most polymers dissolve into solvents endothermically which means their solubility increases on heating. In contrast to this some polymers lose their solubility in water at higher temperatures above a critical point, but regain it on cooling the solvent below the critical temperature. In addition to well known poly(N-isopropyl)acrylamide, water-soluble polymers from a series of N-substituted acrylamide derivatives were synthesized and the characteristic solubity change induced by thermal stimulation was investigated by viscometry, light scattering, NMR and DSC.

Shouei Fujishige

The Measurement and Meaning of Rate Coefficients in Free-Radical Polymerizations

Radical Polymerizations

New experimental data and theory are reported for obtaining three types of rate parameters controlling kinetics and molecular weight distributions in free-radical polymerizations. (1) (a) Propagation rate coefficients (kp) for butyl aery late are found using pulsed-laser polymerization, with the novel variant of carrying out the procedure at very low temperatures (−10 to −40 °C); this obviates some problems hitherto found with the technique, (b) A means of calculating kp from first principles from transition state theory is given, using accurate quantum mechanical computation of the transition state properties. These calculations give quantitative accord with experiment for ethylene, and reveal that the magnitude of the frequency factor for propagation is dominated by three hindered rotors in the transition state. Since these rotations are influenced by the penultimate unit, this suggests that significant penultimate unit effects are likely in copolymerizations. The effect of these rotations also explains the observed effect of deuteration on kp. (2) A new technique for measuring the transfer rate coefficient (ktr) is presented: initiation by pulsed laser, whence ktr can be obtained from the high molecular weight slope of a plot of ln(number molecular weight distribution) against molecular weight. The method, which can be employed even when extensive termination is taking place, is tested with transfer from MMA to triethylamine. (3) The rate coefficient for termination can be successfully modelled from a knowledge of the diffusion coefficients for oligomeric species as functions of the degree of polymerization and the polymer fraction. New PFG NMR diffusion data for a series of model compounds in polystyrene/benzene give results for this dependence which are in accord with a semiempirical scaling law suggested previously [Piton MC, Gilbert RG, Chapman BE, Kuchel PW (1993) Macromolecules 26: 4472], suggesting that this scaling should be a useful basis for predicting termination rate coefficients.

Johan P A Heuts, Paul A Clay, David I Christie, Mark C Piton, Jelica Hutovic, Scott H Kable, Robert G Gilbert

Structure-Reactivity Relationships in Acyclic Diene Metathesis (ADMET) Polymerization

The structure/reactivity behavior for pure hydrocarbon diene monomers, and for dienes containing heteroatoms has been examined. Steric hindrance is the controlling factor for hydrocarbon monomers, and intramolecular electronic interactions determine the reactivity of dienes possessing heteroatom functionality. This electronic interaction phenomenon is termed the “Negative Neighboring Group Effect”.

K. B. Wagener

In-Situ Spectroscopy of Redox Reaction in PPY

In-situ Raman spectra of PPy are obtained with excitations of 514.5 and 1060nm. Strong Raman scattering observed with a deep reduction at 514.5nm excitation coincides with the degree of transparency of PPy of which color turns into pale yellow from dark on the reduction. The Raman scattering intensity of PPy with the deep reduction is 10 folds stronger than that of fresh PPy. The intensity enhancement of the Raman spectra with 1064nm excitation is insignificant but the spectra reveal much more information than those with 514.5nm excitation. Conjugation length generally shortens at the early stage of reduction but recovers on prolonged reduction with 1064nm excitation. Reduced PPy is easily oxidized after cutting-off the applied potential and the Raman spectrum of reduced PPy left in the system for 30min is almost the same as that of fresh PPy.

D. Y. Kim, D. H. Kim, J. Y. Lee, C. Y. Kim

Disubstituted Poly (Bithiophene) s: Syntheses and Applications

The properties of electrochemically prepared poly(3,3′-dichloro-2,2′-bithiophene) (PDCBT) and poly(3,3′-dibutoxy-2,2′-bithiophene) (PDBOBT) were studied and compared with polybithiophene (PBT) in order to investigate the influence of different substituents. Smaller band gap and enhanced neutral-to-doped transition were observed in PDBOBT, whereas PDCBT was characterized with larger band gap and relatively unstable doped state.Polybithiophene film coated on indium tin-oxide (ITO) glass plate was used to detect low levels of ascorbic acid based on changes in the UV-visible absorption characteristics of the doped polymer. To further investigate the influences of substituents on polybithiophene, both PDCBT and PDBOBT were used to detect ascorbic acid and the performance of these sensors were evaluated.

H. S. O. Chan, S. C. Ng, H. H. Huang, S. H. Seow

Fluorescence Studies of Polymer Diffusion Across Interface

We investigate the influence of surface properties on the kinetics of polymer diffusion across interfaces of films prepared from several different types of poly(n-butyl methacrylate) [PBMA] core-shell latex particles. A series of core-shell PBMA microspheres containing different amounts of methacrylic acid groups in their shell were prepared by three- stage emulsion polymerization. PBMA latex with poly(ethylene oxide) [PEO] chains at the surface was prepared by dispersion copolymerization of BMA with PEO macromonomer. Each pair of latex, one labeled with a donor (phenanthrene), the other, with an acceptor (anthracene), allows us to use direct non-radiative energy transfer experiments to follow polymer interdiffusion in their latex films. The interdiffusion was found to be significantly retarded but not suppressed, either by the presence of the acid groups in the latex shell, or by their salts. Neutralization of the acid groups by Ba2+ had a larger effect than Na+ on slowing down the polymer diffusion. On the other hand, PEO chains at the latex surface was found to promote interdiffusion in the early stages of film formation and aging.

Mitchell A. Winnik, Haeng-Boo Kim, Seigou Kawaguchi

Recent Studies on β-Crystalline Form of Isotactic Polypropylene

Isotactic polypropylene shows four distinguishable chain conformation with each being a 2 × 1/3 helix1. Different packing geometries lead to three well known crystalline structures (polymorphs), namely the monoclinic α-form, the hexagonal β-form and the triclinic γ-form. The appearance of these structures is critically dependent upon the ciystallization conditions1–5. Among these three crystalline structures, the monoclinic α-form is by far the most common, being found in normal melt-crystallized or solution-crystallized IPP samples. In the industrial practice, therefore, β- and γ-form have been considered as laboratory curiosities2. The practical way for obtaining β-form with relative high purity is to use nucleating agent. Only a few materials are known to nucleate β-form spherulites6,7.

Guanyi Shi

Controlling Sequence Distribution in Copolyesters

Recent progress on elucidating the role of interchain transesterification reactions in the copolyesters is described. New data are presented supporting the chemical nature of the ordering process. An unexpected degradation reaction in the p-hydroxybenzoic acid/2,6-hydroxynaphthoic acid copolyester system is discussed.

C. W. Potter, J. C. Lim, G. Serpe, J. Economy

Performance on Demand — A New Era in Polymer Science (A Case Study Using Conducting Polymers)

The notion of Performance on Demand is not alien to polymer research scientists. Usually however, the demand has come from engineers and has been aimed at the polymer scientist with a view to achieving a desired level of performance from both researcher and material. In most instances the time lag associated with the demand and the response has been much longer than either the engineer or the researcher would like.

G. G. Wallace

Reversible Optical Storage in Azo Polymers

Amorphous high-Tg azobenzene-containing polymers can be used as reversible information storage materials in form of films. The procedure takes advantage of the photochemically activated trans-cis-trans isomerization of the azobenzene groups. The written information is stable below the polymer glass transition temperature. Writing and erasing can be performed up to 105 times on the same spot or the polymer film. The reorientation mechanism depends on the type of substituents bound to the azobenzene group, on the type of the neighboring group on the polymer chain and on the tendency of the polymer to self-organize. The efficiency of the process depends on the maximum absorbance of the azobenzene group and can be tailored to reach unity. This property of azobenzene-containing polymers can be used in optical and holographic memory, waveguides and sensors, and photonic devices.

A. Natansohn, P. Rochon

Highly Electrically Conductive Polymer Composites and Blends

Conducting polymers have received a great deal of attention during the last decade because these polymers are considered as promising new materials of many potential applications, in which the polymeric materials have not been considered to be applicable before. Among the various conducting polymers polypyrrole has recently attracted much interests because of its high electrical conductivity combined with its good overall environmental stability.

T. J. Kang, Y. Miyaki, J. H. Han, T. Motobe, Y. E. Whang, S. Miyata

Single-Chain Single Crystal

A new method that makes use of monomolecular patches on a liquid surface has been developed for the crystallization of single chain, and single-chain single crystals of poly(ethylene-oxide) and isotactic polystyrene were investigated. The molecular mass and molecular mass distribution of samples could be found to match a statistical analysis of single-chain particles. The observations of morphology and electron diffraction indicated that single-chain particles are crystals, even single crystals. The observed single-chain crystals have very regular morphology, and several new kinds of morphologies were found for the first time. Proof was brought that the single-chain single crystals do not reach equilibrium state on crystallization, rather assume the lamellar morphology with chain-folded macroconformation, also known from crystallization of polychain crystals.

Haishan Bu, Erqiang Chen, Shengyong Xu

Polymers in New Water Treatment Technologies

New methods of water and wastewater treatment are emerging from CSIRO which have high rates of both reaction and separation. The role of polymers in novel adsorption and coagulation technologies and the influence of polymer structure on performance are reviewed.

B. A. Bolto

Novel Application of Natural Rubber Latex as Natural Flocculant for Tin Tailings Slurry

Natural rubber (NR) latex concentrate is essentially a stable dispersion of polyisoprene latex particles in an aqueous serum phase containing some minor constituents of soluble non-rubbers whereas tin tailings slurry is a very stable dispersion of mainly submicron size clay minerals with some heavier silt particles which normally settle out relatively fast. Under normal pH conditions, the negatively charged clay particles in the slurry would remain disperse for an extended period of time. There has not been much success in destabilizing this slurry with most of the common synthetic polymeric flocculants. It was found that when used in combination with an inorganic salt (e.g. calcium chloride) under optimum conditions, the negatively charged natural rubber latex particles can function as a polymeric flocculant in bringing about a complete heterocoagulation of the mixed dispersions whereby producing a clear supernatant and a porous sediment. The effect of pH, slime and latex concentrations on the heterocoagulation behaviour of the latex-slurry mixed dispersion was investigated. The influence of these factors on the efficiency of destabilization, the floe size of the sediment and the settling rate was compared with those which use calcium chloride only as coagulant. The floe size of the heterocoagulated latex-slurry mixtures decreased with increasing pH of the dispersion and slime concentration. The slurry could not be destabilised effectively using either latex or coagulant alone.

C. C. Ho, K. C. Lee, E. B. Yeap

Liquid Natural Rubber: Preparation and Application

Liquid natural rubber (LNR) is a modified form of natural rubber (NR) with a shorter polymeric chain. The preparation of LNR can either be done via mechano-oxidation or redox reaction or photosensitized oxidation. Mechanooxidation, being the earliest method to be developed, is still widely used with some modifications. Pilot plant scale has already been tested on two redox reaction methods using phenylhydrazine-air and sodium nitrite/chlorite - hydrogen peroxide as oxydo-reducing couples. Photosensitized oxidation of NR is made possible by using a photosensitizer which is active in visible light and able to induce degradative oxidation. Research in the field is quite active but so far no method has developed into a commercial scale. The short nature of the LNR polymeric chain allows many chemical modifications possible and thereby enlarging the field of applications of NR. The potential applications of LNR are in the preparation of thermoplastic NR, adhesives, binders, bitumen, low hardness vulcanizates, paints and varnishes.

Ibrahim Abdullah

A Nuclear Magnetic Resonance Study of the Microstructure of Poly (Vinyl Alcohol)

The microstructures of Poly (vinyl alcohol) (PVA) and Poly (vinyl alcohol-acetate) copolymers were studied by ID and 2D NMR techniques. The assignments of all CH proton resonances of PVA relating to 1,2-1,4-glycol and terminal 1,2-glycol linkages were made. The concentrations of 1,2-glycol linkages located at inner and terminal positions of a polymer chain were determined to be ca. 1.61 and 0.06mol%. End-groups of PVA, which were arising from chain-transfers to solvent, monomer and initiator or from the termination of hydrogen abstraction, could be readily determined by using α,α,β— trideuterated PVA. The short chain branches consisted of two monomer units (butyl branches) resulting from intramolecular chain-transfer to methine carbons have been also identified. Other structural irregularities, polyene structures which arising from heat treatment, were analyzed by 2D COSY NMR spectroscopy. The sequence distributions of (PVA-Ac) copolymers were studied by 13C-NMR spectroscopy. In the saponification reactions of poly(vinyl acetate), the presence of an irregular bonding could make the rate of saponification more slowly. The relationship between the sequence distribution and a saponification distribution was also discussed and the saponification distribution of (PVA-Ac) copolymers could be evaluated from a block character η which is obtained by 13C-NMR spectroscopy. Combination of 1D and 2D NMR technique provides a powerful method for gaining information on the microstructure of these polymers.

S. Amiya

Enhancing Reinforcement Effects of Polymers in Asphalt: An Applied Approach to Solid Waste Disposal

Polyethylene, a recyclable waste which is abundantly available either as virgin off specification material or from solid waste classification processes, was slightly chlorinated to improve its compatibility with asphalt. High density polyethylene, HDPE, and chlorinated polyethylene (CPE) modified asphalts were evaluated using dynamic mechanic analysis (DMA), DSC, and epifluorescence microscopy. The results confirm that CPE’s with low chlorine contents (<15 wt %) are more compatible with asphalt than HDPE. Blends with up to 20% ground vulcanized rubber (both crumb and 200 mesh powder particles) from recycled tires were prepared with asphalt cements of various grades (AC5 – AC30) and evaluated using DMA. Blends produced from powdered rubber particles exhibited Newtonian behavior at high temperatures; similar behavior was not observed with crumb rubber blends. The mechanical properties of asphalt-rubber mixtures depended upon the concentration of rubber additives, the particle dimensions, and the chemical composition of the asphalt. Some asphalts induced excessive swelling of the rubber particles; blends with high temperature viscosities substantially greater than the upper limit of 3 Pa·sec resulted. The dynamic mechanical characteristics of all blends are discussed in terms of G*/sin δ and G″; comparative data are presented according to the new SHRP binder specifications. Constant stress creep and creep recovery of the polymer or rubber asphalt blends proved to be a sensitive measure of the additive content.

William H. Daly, Zhaoyao Qiu, Jeffrey Youngblood, Ioan Negulescu

Rigid-Rod Polyimides with n-Alkoxymethyl Side Chains

Three series of new polyimides were prepared by condensation of imidazole-blocked 2,5-bis(n-alkoxymethyl)-1,4-benzene diisocyanates with pyromellitic dianhydride (PMDA), benzophenone tetracarboxylic dianhydride (BPDA), and naphthalene tetracarboxylic dianhydride (NTDA), respectively. After the polymers obtained were spectroscopically characterized, their solubilities, thermal properties and crystalline structures were measured and discussed. It was found that structures and properties of the polyimides having regularly substituted n-alkoxymethyl(n-CH2OCmH2m+1, m=4, 6, 8) side branches are governed not only by side chain length, but also by main chain rigidity.

S.-B. Park, Y.-J. Choi, W.-C. Zin, J. C. Jung

New Developments in Perfluoroelastomers: Chemistry, Properties and Applications

Two new perfluoroelastomer crosslinking systems have been developed, one based on the carbon-hydrogen (C-H) functionality and the other on high energy irradiation. The hydrogen atoms located between fluoro-substituted methylene groups are acidic and react with strong nucleophiles. A dinucleophile, which is also a strong base, first abstracts the acidic hydrogen, giving an anion on the backbone which, in turn, eliminates a fluoride anion to generate double bonds across which the dinucleophiles then add to make a crosslinked network. Tensile properties, compression set resistance and thermal resistance are excellent and compare favorably with previously developed crosslinking systems. Crosslinking by high energy irradiation, e-beam or γ-irradiation, is carried out on preformed articles and requires no chemical reagents or high temperatures. Doses of 10–15 Mrads are adequate and there is little selectivity in terms of efficiency among polymers containing various functionalities. Some chain scission also occurs. The crosslinks appear to be carbon-carbon bonds.

Anestis L. Logothetis

Oriental Lacquer

The oriental lacquer is prepared from the sap of the “varnish tree” Rhus verni-ciflua, which is an emulsion of an aqueous phase and an organic phase called urushol. The urushi fraction consists of a mixture of catechol derivatives substituted in 3-position with aliphatic C15 or C17 side chains. About 60% of these side chains are trienes. The structure of the trienes is similar to that in linseed or tung oil and is essential for the effectiveness of the oxidative curing of oriental lacquer. We have utilized new techniques and used combinations of modern techniques to analyze the urushiol mixtures and to characterize and identify each individual compound. We have also developed ultraviolet stabilizers for oriental lacquer, stabilizers that could be incorporated into the polymerizing mixture during the curing process to result in ultraviolet stabilized oriental lacquer.

Otto Vogl, Jan Bartus, Meifang Qin, John D. Mitchell

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