Thermal Properties of N-Phenylmaleimide-Isobutene Alternating Copolymers Containing Polar Groups to Form Intermolecular and Intramolecular Hydrogen Bonding

Abstract

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 )...

Thermally Stable Fluorescent Maleimide/Isobutene Alternating Copolymers Containing Pyrenyl and Alkynylpyrenyl Moieties in the Side Chain

“…[21][22][23] Recently, it was reported that the alternating copolymerization of N-alkylmaleimides (RMI) with isobutene (IB) produced high-molecular-weight copolymers [poly(RMIalt-IB)s] with excellent thermal stabilities, as well as excellent mechanical and optical properties. [24][25][26][27][28][29][30] For example, the onset temperature of the thermal decomposition was over 350 8C and the glass transition temperature (T g ) was 152 8C for poly(RMI-alt-IB) with an N-methyl substituent. [24] The mechanical and optical properties were also reported to be similar or superior to conventional transparent polymeric materials, such as poly-(methyl methacrylate) and polycarbonate bisphenol-A; the flexural strength and modulus were 137 MPa and 4.81 GPa, and the refractive index and Abbe's number were 1.53 and 51, respectively, for the same poly(RMI-alt-IB).…”

Thermosetting Maleimide/Isobutene Alternating Copolymer as a New Class of Transparent Materials

“…The characteristic peaks observed in this study were similar to those for the alternating copolymers obtained by the copolymerization of various RMIs and IB. [18][19][20][21][22][23][24][25] In the spectrum shown in Figure 1, no peak was detected for the unreacted maleimide residue, although it is expected to be observed at 6.72 ppm if the allyl group of the AMI K. Takeda, A. Matsumoto Table 1. Radical copolymerization of AMI with IB in 1,2-dichloroethane at 30 8C a) .…”

“…It has been pointed out that some allyl compounds are polymerizable and their propagation cannot be negligible under several polymerization conditions. [2,[30][31][32] In the present study, the allyl propagation and the addition of the allyl radical to the maleimide are not important for determining the copolymer structures because of the used copolymerization conditions with a large excess amount of IB (k 23 [IB] >> k 21 [MMI]). Actually, Equation (5) can be used only for the copolymerization conditions using a low MMI concentration.…”

“…This solubility was the same as that of the other poly(RMI-alt-IB)s with N-alkyl substituents, as previously reported. [20][21][22][23] After heating poly(AMI-alt-IB), the copolymer became insoluble in all the solvents. Figure 4 shows the results for the TG measurement of poly(AMI-alt-IB) in a nitrogen stream at the heating rate of 10 8C Á min À1 .…”

“…Doi et al and we have already reported various kinds of alternating copolymers of N-alkylmaleimides (RMI) with isobutene (IB) [poly(RMI-alt-IB)s] having excellent thermal stabilities, as well as excellent mechanical and optical properties. [18][19][20][21][22][23][24][25] The poly(AMI-alt-IB) obtained in the present study includes an unsaturated group in the N-substituent, which is curable We synthesized an alternating copolymer of N-allylmaleimide (AMI) and isobutene (IB) [poly(AMI-alt-IB)] as a new class of thermosetting polymers by the free radical copolymerization process. The reactivity of the maleimide group of the AMI monomer was evaluated to be 10 3 times higher than that of the N-allyl group based on the results for the ternary copolymerization system composed of N-methylmaleimide (MMI), N-allylphthalimide (AP), and IB.…”