The radical copolymerization of N-methyl, ethyl, n-butyl, and 2-ethylhexylmaleimides (RMIs) with 1-methylenebenzocycloalkanes (BCms) was carried out to fabricate thermally stable and transparent polymer materials. The copolymerization reactivity of BCms significantly depended on the carbon number of the ring structure of BCms. The analyses of the comonomer–copolymer composition curves and theoretical calculations results revealed that the sequence-controlled copolymerization of RMIs with BCms occurred in alternating and 2:1 fashions according to the BCms reactivity, which depends on the coplanarity of the exomethylene moiety and the benzene ring. The alternating and high-molecular-weight copolymers of BCms and RMIs exhibited excellent thermal and optical properties. We have demonstrated that the radical copolymerization of RMIs is useful not only as the method for high-performance transparent polymer production but also as the tool for the fundamental research of radical polymerization mechanism.

Thermally stable and transparent polymers were synthesized by the sequence-controlled radical copolymerization of N-substituted maleimides (RMIs) with various olefins as well as polyisobutene (PIB) macromonomers. The copolymerization behavior significantly depended on the olefin structures, leading to the formation of AB-alternating and AAB-periodic (2:1 sequence-controlled) copolymers. The sequence-controlled radical copolymerization mechanism was discussed based on the monomer reactivity ratios, which were determined using terminal and penultimate unit models for the copolymerization systems investigated in this study as well as in the literature. The olefin comonomers were classified into several groups according to the copolymerization fashions under the terminal and penultimate unit controls and their conjugated structure and the steric bulkiness of the substituents. The copolymers exhibited excellent thermal properties; the onset temperatures of the resulting copolymers were higher than 300°C, and the glass transition temperature (T g ) values varied over the temperature range of −68 to 210°C, depending on the structure of the N-and α-substituents of the comonomer repeating units.

The radical alternating copolymerization of N‐substituted maleimides (RMIs) with N‐methyl, n‐butyl, and 2‐ethylhexyl groups and styrene derivatives with various α‐substituents (RSs) is carried out. The yield and the molecular weight of the obtained copolymers significantly decrease with an increase in the size of the α‐substituent of RSs, but are independent of the N‐substituents. The glass‐transition temperature of the copolymers increases on the introduction of the large substituents into the RS repeating units. The high‐molecular‐weight poly(RMI‐alt‐RS)s are soluble in organic solvents and provide flexible and transparent films with excellent transparency by casting the solutions. magnified image

Spherulitic isotactic polypropylenes (iPPs) having a wide range of β-phase contents were prepared by adding β-nucleators, and the effects of the β-phase modification on the mechanical properties of the iPP were investigated. This chapter described the tensile properties of β-nucleated iPP, while key structural parameters, such as spherulite size and crystallinity, were controlled. The increase in the β-phase content led to broader yield peaks and an enhancement in the yield toughness but to a reduction in the yield strength. On the other hand, the initial elastic modulus was found to be independent of the β-contents. Furthermore, the deformation of the β-spherulites, which have a sheaflike structure, was anisotropic and depended on the stretching direction with respect to the sheaf axis. Consequently, the improved drawability and ductility of β-iPP compared to α-iPP are thus associated with the enhanced toughness resulting from the multiple deformation processes in the sheaflike spherulites.

Fig. 1. Chemical structure of carboxyl-terminated butadiene-acrylonitrile (CTBN).