Synthesis, characterization, and application of a bifunctional coupler containing a five- and a six-membered ring carbonate
Introduction
The chemistry of cyclic carbonates, which has been studied since the 1930s, has come to be an interesting area of research within the past 30 years [1]. Polymers bearing carbonate groups either in the main or in the side chains attracted much attention because of their application as biocompatible, optical, high dielectric, and/or adhesive materials [2], [3]. Cyclic carbonates undergo both anionic and cationic ring-opening polymerizations. The polymerizability, however, depends on the ring-size. Six-membered cyclic carbonates result in the corresponding polycarbonates by anionic or cationic ring-opening polymerization [1], [4], [5], [6], [7], [8], [9], [10], [11], [12]. However, five-membered cyclic carbonates are thermodynamically stable and do not result in the corresponding polycarbonates; instead poly(ether carbonate)s are obtained by partial decarboxylation [13], [14]. Cyclic carbonates, even substituted five-membered cyclic carbonates, react efficiently with amines to afford the corresponding hydroxyl urethanes, [15], [16], [17], [18], [19]. The reactivity of cyclic carbonates toward amines, however, is also dependent on the ring-size. Under the same reaction condition the rate constant (k) for the bimolecular reaction of six-membered ring carbonates with amines is ca. 29–62 times larger than that of five-membered ring carbonates depending on the reaction temperature [17], [18], [19].
Due to the different reactivity of substituted five- and six-membered ring carbonates these molecules are interesting candidates for bifunctional couplers. A coupler is a molecule, having two or more functional groups that can be addressed selectively so that different functionalities are combined within one molecule. With the help of couplers, the properties of a multifunctional polymer can be tailored. In the past, a series of asymmetric A,A′-carbonate couplers (A1–A4) were developed in our group to selectively combine monodisperse functional amine building blocks and polymers bearing amine groups within a single molecule (Fig. 1) [20], [21], [22], [23], [24]. At low temperatures (0–25 °C) the more reactive functional group (phenyl carbonate group or chloroformate group) was substituted selectively with hydrophilic, hydrophobic or ionic primary amines to result in functionalized couplers, or with a polyamine to result in a polyamine–coupler-adduct. Then, at higher temperatures (60–80 °C) the resulting functionalized couplers are reacted with a polyamine respectively the polyamine–coupler-adduct is reacted with functional amine building blocks. During this reaction the carbonate ring is opened and a urethane group with an adjacent hydroxyl group is formed. These couplers were successfully used for modification of branched polyethyleneimine (B-PEI) [25], [26], [27] and chitosan [28]. In comparison to the couplers A1–A4, couplers bearing five- and six-membered cyclic carbonates have significant advantages. The couplers A1–A4 converted amines first via substitution reaction leading to the release of phenol or hydrochloric acid; this in some cases may be unacceptable. Couplers with two cyclic carbonate groups react with amines only by addition reactions, without the formation of side products.
Monomers bearing five- and six-membered cyclic carbonate groups were polymerized via anionic ring-opening polymerization resulting in polymers bearing carbonate groups in the back bone and five-membered ring carbonates in the side chain [29]. Monomers bearing two six-membered cyclic carbonates and monomers bearing two five-membered cyclic carbonates were used for the preparation of poly(hydroxyl urethane)s [1], [16], [17], [19], [30], [31], [32], [33], [34], [35]. However, the preparation of poly(hydroxyl urethane)s from monomers bearing five- and six-membered ring carbonates was not reported.
In this work a monomer bearing a five- and a six-membered ring carbonate (BC56) was synthesized, characterized and its potential for the preparation of multifunctional polymers was studied. From this monomer functional couplers with ionic, hydrophilic and hydrophobic groups were synthesized. Model reactions of the functional couplers with primary amines were carried out. The use of this monomer for the synthesis of poly(hydroxyl urethane)s via polycondensation was tested. The influence of solvents, temperature, ratio of BC56/diamine, and the nature of the diamine on the molecular weight of the polymer were determined. The hydrolytic stability of BC56 and of functional coupler prepared form BC56 was determined. It is our goal to find suitable couplers/functional couplers, which can be used in a solvent promoting self-association during the synthesis of multifunctional polymers.
Section snippets
Materials
Ethyl chloroformate (Acros Organics, 99%), 2-allyl-2-propyl-1,3-propanediol (Aldrich, 98%), triethylamine (Fluka, 99.8%), 3-chloroperoxybenzoic acid (Acros, 70–75%, m-CPBA), 3-dimethylamino-1-propylamine (Aldrich, 99%), iodomethane (Aldrich, 99%), dodecylamine (Acros, 98%), Jeffamine® M1000 (Huntsman), lithium bromide (LiBr), hexane-1,6-diamine (Aldrich, 98%), 4,9-dioxadodecane-1,12-diamine (BASF, 99%), triethylenetetramine (Aldrich, 98%), N-methylpyrrolidinone (Acros, 99%, NMP), dichlormethane
Results and discussion
Five-membered cyclic carbonates and six-membered cyclic carbonates have different reactivity toward primary amines. This special property enables a coupler containing both cycles – 5,6-coupler (Scheme 1) – to be used for a selective linking of two functional amines (RF1–NH2 and RF2–NH2) within one molecule and to form a bis(functional) compound. On the other hand, both five- and six-membered cyclic carbonates react with primary amines. Reacting with a diamine, hydroxyl functional polyurethanes
Conclusion
Bis(cyclic carbonate) coupler BC56 bearing a five- and a six-membered carbonate ring was successfully synthesized and characterized. It was evidenced by means of model reactions that the reaction of BC56 with 1 eq. primary amine proceeds highly selective, only/mainly the six-membered cyclic carbonate was converted. Functional couplers with hydrophobic, ionic, and hydrophilic groups were prepared starting with BC56 and corresponding primary amines. In a later step the five-membered carbonate ring
Acknowledgements
The authors thank the Bundesministerium für Bildung und Forschung (Project No. 03X0019D) for the financial support.
References (40)
Prog. Polym. Sci.
(2000)Prog. Org. Coat.
(2003)- et al.
Prog. Polym. Sci.
(2005) - et al.
Polymer
(1995) - et al.
Catalytic conversion of carbon dioxide to polymer blends via cyclic carbonates
- et al.
Die Makromol. Chem.
(1992) - et al.
Die Makromol. Chem.
(1990) - et al.
Macromolecules
(2001) - et al.
Macromol. Rapid Commun.
(2007) - et al.
Macromol. Chem. Phys.
(1995)
Macromolecules
Macromolecules
Cyclic carbonates
Die Makromol. Chem., Rapid Commun.
Die Makromol. Chem.
Macromol. Rapid Commun.
Macromol. Chem. Phys.
J. Polym. Sci., Part A: Polym. Chem.
J. Polym. Sci., Part A: Polym. Chem.
J. Polym. Sci., Part A: Polym. Chem.
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