Study of the thermal degradability of poly(α‐methylstyrene) with modified end groups

Abstract

To induce degradabilities in polymers in response to environmental conditions, endmodification reactions of poly(a-methylstyrene) (PMS) derivatives were carried out. 2-Phenylallyl halide derivatives such as 2-phenylallyl bromide, 2-@-tolyl)allyl bromide, and a-trifluoromethylstyrene were found to be suitable end-modification agents. For example, the o-2-phenylallyl-PMS derivative was prepared with almost quantitative functionali1.y by the reaction of the living PMS derivative with 2-phenylallyl bromide. In a similar way, o3,3-difluoro-2-phenylallyl-and o-2-(4-tolyl)allyl-PMS derivatives were synthesized. Based on thermogravimetric analysis, the onset of the degradation temperature of the endmodified PMS derivatives decreased in the following order: o-hydrogen-> w-3,3-difluoro-2-phenylallyl-> o-2-phenylallyl-> o-2-@-tolyl)allyl-PMS. Actually, the onset temperature of w-2-@-tolyl)allyl-PMS derivatives was 50 "C lower than that of o-H-PMS derivatives. These results indicate that the active species is produced effectively at the endunsaturated bond, which initiates depolymerization of the polymer at rather low temperatures. Therefore, it is concluded that a 2-phenylallyl substituent at the end of the PMS chain induces effective degradation through a radical mechanism.

Synthesis of 2-Phenylallyl-ended Ply(.ALPHA.-Methylstyrene) and Application for Electron-Beam Resist.

“…As we reported previously [7] [8], the end modification of PMS by 2-phenylallyl group was effective to the EB exposure.…”

“…According to this idea, we prepared several types of uniform size PMS with end reactive group such as 2-phenylallyl, 2-tolylallyl and 2-phenyl-3,3-difluoroallyl groups. [7] The end reactive PMS derivatives thus prepared were susceptible against certain stimuli such as heating, acid and base treatments. For example, the onset temperature of the thermal degradation of PMS derivatives with a 2-phenylallyl end group was more than 50 °C lower than that of hydrogen terminated polymer.…”

“…Materials: Purifications of commercial THE (Wako), and a -methylstyrene (MS; Wako) were described in our previous paper. [7] Sec-Butyllithium (sec-BuLi; Aldrich; in cyclohexane) was used as received. The concentration of which was determined by GC, viz, sec-BuLi was reacted with 1,1-diphenylethylene (DPE), then the unreacted DPE was quantified by GC.…”

2-Phenylallyl-ended Poly(.ALPHA.-Methylstyrene): A New Positive Electron-Beam Resist.

“…According to this idea, we prepared several types of uniform size PMS with an end reactive group such as the 2-phenylallyl group, 2-tolylallyl group and 2-phenyl-3,3-difluoroallyl group. [ 10] The end-reactive PMS derivatives thus prepared were susceptible against certain stimuli such as heating, acid and base treatments.…”

“…Materials: Purifications of commercial THE (Wako), and a-methylstyrene (MS; Wako) were described in our previous paper. [ 10] sec-Butyllithium (sec-BuLi; Aidrich; in cyclohexane) was used as received, the concentration of which was determined by a gas chromatography technique, viz, sec-BuLi was reacted with 1,1-diphenylethylene (DPE), then the unreacted DPE was quantified by GC. 2-Phenylallyl bromide (PAB) was prepared according to the literature.…”