Radiation Effects in Polymeric Materials

The origin and existence of life on Earth owe to the presence of radiations that triggered photochemical transformations for sustainable life forms. The classification of radiations into ionizing and non-ionizing radiations, on the basis of interaction with matter, distinguishes their role in the evolution of the environment and its components. With advancement in scientific knowledge, there has been vast development in technological processes that utilize radiations for human benefits. But sometimes radiations pose to be potential risk for environment especially when used as weapon for mass destruction and during human negligence leading to catastrophic disasters.

The material properties can be modified/tailored by either of the techniques available such as top-down method, bottom-up method, composite ratio variation, doping of a suitable dopant, ion beam-related methods and many others. The modifications by ion beam and radiation treatment are quite effective techniques to calibrate the physical, chemical, surface and structural properties of the materials. Polymeric materials are highly radiation sensitive and their properties can be modified by exposing the material to different ions and radiation such as gamma rays, electron and proton beams as well as swift heavy ions. The focus of the present discussion is pointed towards the radiation (mainly swift heavy ions and gamma rays) induced modification of polymeric materials and their physical and chemical aspects. The fundamental concepts of energy transfer of swift heavy ions and the post-irradiation effects such as cross-linking and chain scissoring of polymeric materials have been discussed in this chapter. The polymeric chain scissoring and cross-linking are related to the structural, chemical, surface, electrical and free volume properties of the polymers. The concept of free volume is further related to gas diffusion and separation properties of some of the polymers. The discussion is limited up to the radiation-sensitive polymers such as polymethyl methacrylate, polyethylene terephthalate and polyallyl diglycol carbonate polymers in the present chapter. The applications related to ion beam technology have been discussed in the last section of this chapter.

The chapter presents an overview of the effects and phenomena leading to structural and compositional evolution of polymer materials under high-fluence ion implantation. Ion stopping mechanisms and degradation of polymer structure due to radiation damage are discussed, giving examples for different ion species and polymer types mostly focusing on the low- to medium-energy regimes. Typical depth profiles and tendencies in depth distribution of impurities as well as the related changes in composition of the implanted layers are analysed. The emphasis is put on the high-fluence implantation of metal ions leading to the nucleation of nanoparticles and formation of composite materials. A special case of cluster ion implantation is also discussed. Change in mechanical, electronic, optical and magnetic properties of the ion-implanted polymers is under the consideration in the final part of the chapter also including a brief overview on applications of these materials.

In this chapter, we review fundamental issues related to the damaging processes of PMMA films induced by high-energy ions with kinetic energies from a few keV to a few GeV, covering the regimes of energy deposition dominated by nuclear collisions and by electronic excitation. Emphasis is given to present an overview of the bond-breaking processes, the changes in the polymer chemical structure, and the corresponding modifications in selected macroscopic physical properties (optical, mechanical, and electrical).

This chapter primarily includes the fundamental concepts related to metal nanoparticles with their unique features followed by importance of incorporating them in polymer matrix and finally considering irradiation as a novel tool to tailor the properties of metal–polymer nanocomposites. These nanocomposites are one of the promising materials which have been used in a wide variety of applications ranging from biomedical to optical and electrical devices to aerospace applications. Ionizing irradiation technique is among the most promising strategies for synthesis as well as to amend the changes in composite material because of the advantage of irradiation process compared to conventional synthesis like chemical, vapour deposition, etc., the process is simple, clean and controlled, carried out without producing undesired oxidants products of reducing agents, avoids the addition of undesirable impurities and produces composites which are highly stable. Irradiation-induced effects on polymer-metal nanocomposites provide unique pathway to control and modify the structural, optical and electrical properties of composites basically required for various applications as per desire. Thus, utilizing irradiations as a novel tool, a systematic study has been done to tune the properties of polymer-metal nanocomposites. Induced changes on structural, optical, and electrical properties have been conferred in this chapter.

This chapter presents the basic concepts of conducting or π-conjugated polymers and their different nanostructures and physico-chemical properties, which ushered in a new era of functional organic materials with potential applications. Most importantly, they can replace the traditional metallic conductors owing to their excellent properties of high conductivity, thermal stability, light weight, low corrosion, high flexibility, ease of synthesis and low cost. The first studied conducting polymer was polyacetylene, and in the last two decades, the most extensively studied conducting polymers are polyaniline (PAni), polypyrrole (PPy) and polythiophine (PTh) and their derivatives owing to their interesting physico-chemical properties. Irradiation on polymers with energetic heavy ions is used to tailor their different physico-chemical properties. The energetic heavy ion irradiation-induced modifications on various properties of polymers depends on various parameters viz. type of energy transferred (i.e., nuclear or electronic) to the target, species of ion and ion fluences. The ion-matter interaction with low energy (eV to keV) range causes implantation of the ions, while ions with high energy (keV to MeV) interaction cause irreversible structural modification along the cylindrical ion track, which is of the order of few nanometers in diameter. The fundamental aspects of ion-solid interaction, different related parameters and models governing the ion-solid interaction have been described in details in this chapter. PPy nanotubes, potential candidate of highly conducting π-conjugated polymers, have been chosen for irradiation at different ion fluences to enhance their structural, morphological, electrical, optical and thermal properties. Room temperature swift heavy ion (SHI) irradiation on thin PPy films (thickness ~30–35 µm) was investigated under high vacuum (~10⁻⁵ Torr) condition by 160 MeV Ni¹²⁺ SHI using various irradiation fluences such as 10¹⁰, 5 × 10¹⁰, 10¹¹, 5 × 10¹¹ and 10¹² ions/cm². High-resolution transmission electron microscopy (HRTEM) was used to investigate the morphological changes of SHI-irradiated PPy nanotubes. The irradiated nanotubes exhibit denser structure, and density is highest at 5 × 10¹¹ ions/cm² irradiation fluence. However, on irradiation with the highest ion fluence of 10¹² ions/cm², the density of irradiated PPy nanotubes is decreased. Up to the ion fluence of 5 × 10¹¹ ions/cm², reduction in optical band gap energy (E_g) of irradiated PPy nanotubes is observed; however, at the investigated highest irradiation fluence of 10¹² ions/cm², value of E_g is found to be higher as compared to the unirradiated PPy nanotubes. Micro-Raman studies exhibit that upon SHI irradiation up to the ion fluence of 5 × 10¹¹ ions/cm², the π-conjugation length and crystallinity of PPy nanotubes are increased. Thermogravimetric analysis (TGA) shows enhanced thermal stability of irradiated PPy nanotubes with increasing ion fluence, while thermal stability of PPy nanotubes decreases at the highest irradiation fluence. The current-voltage (I-V) characteristics for the irradiated PPy nanotubes get enhanced with increasing ion fluence, while their I-V characteristics decrease at the highest irradiation fluence of 10¹² ions/cm². The scaling of modulus spectra of irradiated PPy nanotubes at different irradiation fluences depicts irradiation fluence-independent relaxation dynamics of charge carriers. At the end of the chapter, the challenges in the field of ion-matter interaction in pre-/post-irradiation as well as the processing, characterization and application of the target materials have been discussed.

Nuclear track detector has numerous applications in various fields. The effective use of this detector depends upon the thorough understanding of track parameters of energetic ions. The present study attempts to develop and strengthen this understanding. It describes the various methods to measure bulk etch rate \( \left( {V_{\text{B}} } \right) \) of the detector and track etch rate \( \left( {V_{\text{T}} } \right) \) of the incident ions. Further, it throws light on the other parameters such as bulk activation energy \( \left( {E_{\text{B}} } \right) \), track activation energy \( \left( {E_{\text{T}} } \right) \), sensitivity \( \left( S \right) \), critical angle \( \left( {\theta_{\text{C}} } \right) \) and etching efficiency \( \left( \eta \right) \). Finally, an attempt is made to review the studies related to the impact of different etchants and etchant variables on the different types of CR-39. Based on the observations available in the literature, the comparisons are made among impacts of different etchants on CR-39 and results are compiled. The present review concludes the observations and their relevant impacts.

Hydrogels are three-dimensional polymer structures that can captivate and hold a vast quantity of water. They have superior’s properties such as hydrophilicity, high swelling ability, non-toxic in nature, and biocompatibility which makes them prospective materials for various applications. The concept of graft copolymers in biomedical field developed in the past few ten years and lasts to fascinate researchers working in this sector. Research in this sector is ongoing with the aim of alteration of the inherent properties of polysaccharides after grafting, which offers premises to be pervasive in integrated systems with multiple functionalities or the enhanced properties of one domain. This chapter aims to give comprehensive details about research that have been made on radiation-induced synthesis of polysaccharide-based hydrogels in context to biomedical application. This review also intends to explain the mechanism of radiation-induced synthesis of hydrogels. The effect of various radiation sources such as gamma, microwave, electron, and heavy ions is also discussed. Also, current status and plans of hydrogels are presented along with proper citations extracted from the scientific literature. Moreover, this article provides you with essential information that one’s need to start work in this area.

The exposure of the polymer to radiation results in modification on chemical and physical properties of the polymer. Whenever radiation passes through polymer, the drastic changes in the optical, electrical, thermal, chemical, structural, surface morphological, mechanical and rheological properties due to chain scission, chain aggregation, cross-linking, gas evolution etc. The chain scission process results in the decreases of molecular weight, whereas cross-linking process increases the molecular weight. This chapter deals with the changes in the properties of PC due to the effect of the radiation along with the detailed schematic mechanism.

Development in science and technology has made human life much simpler, but evolution and progress of time as well as increasing human demand have generated problems related to energy, health [1], etc. Progress in science and technology is trying to solve these issues to make the human life more comfortable. Growing requirement of biomedical devices, replacement of body parts after their failure, body implants [2, 3], bio-separation, sterilizations [4, 5], biosensors, etc. [6, 7], have shown need of development of advance smart materials (biomaterials). The choice of any material to be used as biomaterial/biomedical applications [8] depends on physical, chemical, surface, and biological properties, i.e., the presence of functional groups, surface free energy, hydrophilicity, surface morphology affects use of any material as biomaterial [9]. In other words, materials having high bio-adoptability and biocompatibility can only be used as biomaterials [10, 11]. Polymers arise as a suitable alternative of conventional biomaterial from last few decades, for synthesis of important biomaterials in modern manufacturing processes as they offer wide varieties of physical, chemical, biological, mechanical, and elastic properties with good processability. None of the normally available polymers possess surface and chemical properties required for many of biomedical applications. Nanomaterials and low-temperature plasma processing offer a novel route for surface and chemical modification in controlled manner without affecting their bulk properties [12]. Plasama processing can be utilized in various pathways to control the desired properties of modified materials, makes plasma so important that we can say “Plasma will future: Plasma for mankind.” Present work shows efficient and relevant route for synthesis of nanobiomaterials using nanotechnology and plasma processing to fabricate biomedical devices for biomedical applications [13].

Polymers have been widely utilized in various applications due to their low cost and easy processability and thus could be utilized in radiation-prone areas for their radiation-resistant behaviour. Ionizing radiations induce chemical kinetics in the polymers leading to the exchange reactions causing the variations in structural conformations. Neutrons since the discovery in 1932 have been posed as a special particle due to its neutral behaviour and hence been utilized in many medical and industrial applications. The neutral behaviour provides it a greater penetration depth and therefore more quantitative measurements to greater accuracy. This chapter has been devoted to review the influence of neutrons in various polymers for their utilization in apron making for radiation workers and neutron dosimetry. Special attention has been paid to the structural elucidation and reactivity of ionized molecules upon exposure of the polymers to the neutron beam. Recent developments in utilizing the neutron irradiation for modifications and upgrading the properties of polymers have also been discussed.

Review on application of radiation for processing of polymers is presented. The radiation sources like gamma irradiators, electron accelerators and accelerator-based e⁻/X systems are shortly discussed. Then, the basic information regarding physical and chemical processes undergoing in the irradiated polymers is presented. Finally, the application of radiation technology in cable, rubber and healthcare industry is reviewed; the well-established technologies exist nowadays and are being applied more widely all over the world.

The main interest of this chapter is to understand the fundamental energy loss processes through which incident energetic heavy ions lose their energies in the stopping medium. Fundamentals of ion interaction with matter are discussed where various modes of energy loss processes are explained. In the context of non-relativistic heavy ions, the contribution due to two types of energy loss modes, i.e., nuclear energy loss and electronic energy loss, is discussed in detail. Comparison between nuclear energy loss and electronic energy loss as a function of ion’s energy for Cu ion in Si target is shown. The fundamental Bohr energy loss equation is derived and extended by incorporating various correction terms. The most commonly used semi-empirical/empirical type energy loss formulations (Lindhard et al., Northcliffe and Schilling, Ziegler et al., Paul and Schinner, Huber et al., and Diwan et al.) are briefly introduced. Bragg’s rule, which determine the energy loss in polymers/compounds, is discussed. Finally, the importance of energy loss is highlighted.