Thermally stable copolymers with an alternating repeating structure, poly(RMI‐alt‐IB)s, were synthesized by radical copolymerization of N‐substituted maleimides containing a polar group with isobutene. The onset temperature of decomposition was higher than 300 °C and the glass‐transition temperature increased by the introduction of hydroxy and carboxy groups. IR spectroscopic analysis revealed the role of intermolecular hydrogen bonding on the thermal stability of the copolymers. It was also revealed that the amount of water absorbed into poly(RMI‐alt‐IB)s with a hydroxymethyl substituent was as high as 270% of the weight of the used polymer, while the introduction of a carboxy group resulted in lower water absorption properties.

The radical alternating copolymerization of N‐methylmaleimide with various olefins was carried out to obtain thermally stable and transparent polymers. Cyclic olefins including an exo‐methylene group showed high polymerization reactivities during the copolymerization. The introduction of a polar substituent into the olefin monomers results in the formation of copolymers with a high yield. The polymerization reactivity of the olefins is discussed based on DFT calculations. The introduction of cyclic and polar substituents into the olefin repeating units increased the glass transition temperature of the obtained copolymers, similar to the previously reported results for the introduction of bulkier and polar substituents into the N‐substituents of the maleimide.magnified image

We have demonstrated that the alternating copolymers obtained from N-phenylmaleimides having hydroxy and carboxy substituents and isobutene show excellent thermal stabilities; namely, onset temperatures of decomposition higher than 350 C and glass transition temperatures higher than 220 C, depending on the structure and position of the polar groups in the N-phenyl group. The obtained copolymers were soluble in organic solvents, such as dimethyl sulfoxide, dimethylformamide, tetrahydrofuran, and acetone, and transparent and brittle films were obtained by casting from their acetone solutions. The role of intermolecular hydrogen bonding for an increase in the glass transition temperature by the introduction of the polar groups was investigated by temperature-controlled IR spectroscopy. The formation of intramolecular hydrogen bonding for the N-2-hydroxyphenyl derivative was also revealed. The molecular conformations were discussed on the basis of the results of DFT calculations for the model compounds of the repeating unit in the copolymers. Recently, new thermo-resistant polymers with a high transparency attract a great interest as key materials for optoelectronic applications. The radical polymerization and copolymerization of N-phenylmaleimide (PhMI, 1) and the thermal properties of the resulting polymers have been extensively studied in order to obtain thermally stable vinyl polymers.1-3 At the same time, various kinds of PhMI derivatives have also been synthesized and polymerized. [4][5][6][7][8][9][10][11][12] When alkyl substituents were introduced in the N-phenyl group, the polymers were soluble in non-polar solvents and showed an excellent thermal decomposition property, while poly(1) was soluble in limited kinds of polar solvents. 13,14 On the other hand, the introduction of polar substituents resulted in the formation of polymers with poor solubility. For example, thermally stable polymers were synthesized by the polymerization of N-(hydroxyphenyl)-, N-(carboxyphenyl)-, and N-(trifluoromethylphenyl)maleimides, but they were insoluble or had a very limited solubility in solvents. 4,[15][16][17] In 1996, Doi and coworkers reported that the alternating copolymerization of N-alkylmaleimides (RMI) with isobutene (IB) [poly(RMI-alt-IB)] produces high molecular weight copolymers with excellent thermal properties, as well as excellent mechanical and optical properties.18-21 Poly(RMI-alt-IB)s are soluble in a larger number of organic solvents and had a moderate softening temperature. The processing of poly-(RMI-alt-IB)s can be easily carried out for the fabrication of polymer films, sheets, and molded products. Recently, we synthesized the alternating copolymers of RMIs containing a functional group, such as hydroxy and carboxy groups, combined with IB, and revealed the role of the intermolecular hydrogen bond of the functional groups in the thermal properties of the obtained copolymers. 22 We demonstrated that poly(RMI-alt-IB)s containing hydroxy and carboxy groups showed high glass transition temperature (T g )...

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Alternating copolymers of maleimides containing pyrenyl and alkynylpyrenyl moieties with isobutene (IB) were synthesized as a new class of heat‐resistant and fluorescent polymers. N‐(1‐Pyrenyl)maleimide (1) and N‐[4‐(1‐pyrenylethynyl)phenyl]maleimide (2) were copolymerized with IB in the presence and absence of N‐methylmaleimide (3). The obtained maleimide/IB copolymers showed excellent thermal stability and high glass transition temperatures, and were soluble in common organic solvents. The copolymers including the alkynylpyrenyl fluorophore emitted strong fluorescence with a high quantum efficiency (Φ = 0.83) even in the presence of air and upon heating. Solid‐state fluorescence in transparent films was also investigated.magnified image