Toru Doi

Radical copolymerization of N-alkylmaleimides with isobutene and the properties of the resulting alternating copolymers

Radical copolymerization of N-methylmaleimide (MeMI) as well as other N-alkylmaleimides (RMI) and isobutene (IB) was carried out with 2,2′-azobis(isobutyronitrile) as an initiator at 60°C. The initial rate of the copolymerization (Rp) was dependent on the monomer composition and was maximum at the 40 mol % of MeMI in the feed. A solvent effect on the Rp and the monomer reactivity ratio was observed in this copolymerization system, i.e., copolymerization in chloroform produced a higher Rp and an alternating tendency compared with those in dioxane (rMeMI = 0.14, r1B = 0 in chloroform and rMeMI = 0.47, r1B = 0 in dioxane). The alternating copolymer of RMI and IB shows a high glass transition temperature (Tg) and excellent thermal stability, e.g., the Tg and the thermal decomposition temperature (Td) were 152 and 363°C, respectively, for the alternating copolymer of MeMI and IB. Both the Tg and Td increased as the concentration of the MeMI unit in the copolymers increased. Colorless transparent sheets were obtained from press molding the alternating copolymers. They showed excellent mechanical and optical properties.

A new class of transparent polymeric materials. I. Production and properties of an alternating copolymer of N‐methylmaleimide and isobutene

An alternating copolymer of N-methylmaleimide and isobutene was produced by a radical precipitation polymerization method. The copolymer thus produced is a new class of transparent polymeric material that shows a unique balance of optical, thermal, and mechanical properties. The visible light transmittance was more than 90% and the stress optical coefficient was smaller than that of polycarbonate, leading to moldings with lower birefringence. The heat deflection temperature of the copolymer was as high as 157°C, and the thermal expansion coefficient was about 30% smaller than those of poly(methyl methacrylate) and polycarbonate. The copolymer showed excellent mechanical properties, specifically, the flexural modulus was the highest among the typical amorphous polymers.

Alternating copolymerization of N-(alkyl-substituted phenyl)maleimides with isobutene and thermal properties of the resulting copolymers

Radical copolymerization of N-(alkyl-substituted phenyl)maleimides (RPhMI) with isobutene (IB) was carried out with an initiator in various solvents at 60°C. The copolymerization of N-(2,6-diethylphenyl)maleimide (2,6-DEPhMI) with IB in benzene proceeded readily in a homogeneous system to give an alternating copolymer over a wide range of the comonomer compositions in the feed. Whereas the alternating tendency of the copolymerization of other RPhMI with IB decreased depending on the alkyl substituents of RPhMI in the following order : 2,6-DEPhMI > N-(2,6-dimethylphenyl)maleimide ≥ N-(2-methylphenyl)maleimide >N-(4-ethylphenyl)maleimide. The copolymerization reactivities were discussed based on the rate constants for the homo-propagations and cross-propagations. Subsequently, the effect of the solvent on the rate and the reactivity ratios was examined. It was revealed that the copolymerization in chloroform proceeded with higher alternating tendency at a higher copolymerization rate than in the copolymerizations in benzene or dioxane. The copolymers of RPhMI with IB showed excellent thermal stability, i.e., high glass transition temperature and initial decomposition temperature over 200 and 350°C, respectively.

Evident solvent effect on propagation reactions during radical copolymerization of maleimide and alkene

The radical copolymerization of N-(2,6-dimethylphenyl)maleimide (DMPhMI) and 2,4,4-trimethylpentene (TP) was investigated in several solvents at 60°C. The copolymerization rate and the molecular weight of the resulting copolymers were dependent on the kind of solvent used. It was also revealed that the monomer reactivity ratios depended on the solvent; r 1 = 0.086 and r 2 = 0 in chloroform and r 1 = 0.25 and r 2 = 0 in benzene, where DMPhMI and TP are M 1 and M 2 , respectively. The propagation rate constants were determined for the homopolymerization and copolymerization in chloroform and benzene using electron spin resonance spectroscopy. The homo- and crosspropagation rate constants (k 11 and k 12 , respectively) were revealed to depend on the solvent: k 11 is 20 and 37 L/mol.s and k 12 is 230 and 150 L/mol.s in chloroform and in benzene, respectively. The interaction between the maleimide moiety and the solvent molecules was discussed based on the acceptivity of the solvents.

A new class of transparent polymeric materials. II. Synthesis and properties of poly(N‐cyclohexylmaleimide‐alt‐isobutene) modified with lauryl methacrylate

Transparent polymeric materials with high heat resistance and low water absorption were designed based on the alternating copolymers of N-substituted maleimide (RMI) with isobutene (IB). The N-substituent of the maleimide significantly affected the glass transition temperature (Tg) and water absorption of the copolymers. Poly(N-cyclohexylmaleimide-alt-JB) [poly(CHMI-IB)] showed a Tg value as high as 192°C and relatively low water absorption. Furthermore, the incorporation of a small amount of lauryl methacrylate in the copolymers was confirmed to reduce the water absorption of the copolymer drastically, although it decreased the Tg of the copolymers at the same time. Poly(CHMI-IB), containing 4 mol % lauryl methacrylate, showed a good balance of excellent transparency, high heat resistance, acceptable mechanical properties, and low water absorption. The heat deflection temperature was as high as 141°C. The water absorption at 23°C after immersion for 14 days was 0.56% and the dimensional change after 7 days was 0.06%. They are half and one-quarter of those of poly(methyl methacrylate), respectively.

A new class of transparent polymeric materials. III. Miscible blends of poly(N‐methylmaleimide‐alt‐isobutene) with poly(acrylonitrile‐co‐styrene) and the properties of the blends

The blend miscibility of poly(N-methylmaleimide-alt-isobutene) [poly-(MeMI-IB)] with poly(acrylonitrile-co-styrene) (SAN) was investigated by means of measurement of the glass transition temperature of the blends. Poly(MeMI-IB) was found to be miscible with SAN of a specific range of acrylonitrile (AN) contents in the copolymer to produce transparent moldings. The refractive index changed from 1.58 to 1.53 and the dispersion decreased with increasing the amount of poly(MeMI-IB) in the blends. The stress optical coefficient of poly(MeMI-IB) was found to be reduced by the blending of SAN. The glass transition temperature, flexural modulus, and surface hardness of the blends increased with an increase in the amount of poly(MeMI-IB) in the blend.

P-47: A New High Performance Transparent Plastic Film for Flexible Display Substrates

Development of high performance plastic substrates is the key to realize flexible displays. We have been developping a new transparent plastic (OPS: development name) having a unique balance of excellent optical properties, high heat resistance, and practical mechanical strength for flexible display substrates. This paper will report the performance of the new transparent plastic.

P-57: A Transparent Plastic Film having Excellent Optical Properties and High Heat Resistance for Flexible Display Substrates

We have developed a new high performance plastic substrate for flexible displays. The plastic substrate has a multi-layered structure composed of a newly developed base film, hard coat layers and gas barrier layers. The plastic substrate has a unique balance of excellent optical properties, high heat resistance over 200 °C, and practical mechanical strength.

P‐121: Optical Anisotropic Compensator by Polymer Stabilization Technique

Polymer stabilization technique was applied for making optical anisotropic compensators for the purpose of controlling the wave length dispersion characteristic. Quarter wave compensators with hybrid aligned structure were prepared by this technique using liquid crystals (LCs) with different optical birefringence (Δn). The wavelength dispersion of the resulting compensators depended on the Δn of the LC used. The compensator using LC with the smallest Δn was found to give almost same retardation value over the wide range of visible light. Hybrid compensators were combined with hybrid aligned liquid crystal cells for reflective- LCD application. The hybrid compensator with very low wavelength dispersion gave the reversed dispersion characteristics very close to the ideal one at black state.

P-63: A New Transparent Plastic Substrate having High Heat Resistance and Low Retardation for Flexible Displays

We have been developing a new transparent plastic substrate for flexible displays. The plastic substrate (OPS substrate) is composed of a newly developed base film (OPS film) and hard coat layers. The OPS substrate has excellent physical properties such as high transparency, low retardation and high heat resistance over 200°C. The coefficient of thermal expansion (CTE) is relatively low as 40–45ppm. The dimensional changes under various conditions including temperature and humidity were directly observed by using CCD camera. The electrical properties of the OPS substrate sputtered Indium Tin Oxide (ITO) at various temperatures were evaluated. The OPS substrate sputtered ITO at 200°C shows low sheet resistance as 10Ω/□ and it is almost same as that of glass substrate sputtered ITO under the same condition.