Adamantyl-substituted polymers and diphenylethynyl-terminated benzoxazoles

Jennifer Jean Jensen

Abstract

The research presented in this dissertation is from two different areas. The first involves the synthesis of adamantyl-substituted phenolic polymers and a series of copolymers of adamantyl methacrylate derivatives with styrene and methyl methacrylate. Three 4-(1-adamantyl)phenyl methacrylate monomers were synthesized from 4-(1-adamantyl)phenol derivatives which were obtained by Friedel-Crafts alkylation of phenol, 2-methylphenol and 2,6-dimethylphenol with 1-bromoadamantane. 4-(1-Adamantyl)phenol was reacted with formaldehyde using acid as a catalyst to form linear phenol-formaldehyde polymers. Increasing the amount of paraformaldehyde increased formation of cyclic octamer. The cyclic octamer was acetylated to give a soluble model compound for comparison to acetylated polymers. All of the synthetic variations employed produced low molecular weight polymers. The polymers showed number average molecular weights of ca 3000 (versus polystyrene standards by SEC), and exhibited glass transition temperatures ranging from 175-230$\sp\circ$C, ca 100$\sp\circ$ over unsubstituted and para-alkyl substituted analogs. All samples exhibited a 10% weight loss at 400$\sp\circ$C in nitrogen. Copolymers of the adamantyl methacrylate derivatives with styrene were synthesized using free radical techniques, and one copolymer series of 4-(1-adamantyl)phenyl methacrylate was also made with methyl methacrylate. Values of r$\sb1$ (styrene) and r$\sb2$ (the three methacrylate monomers) were: r$\sb1$ = 0.22 and r$\sb2$ = 1.51 for 4-(1-adamantyl)phenyl methacrylate copolymers, r$\sb1$ = 0.31 and r$\sb2$ = 2.44 for 2-methyl4-(1-adamantyl)phenyl methacrylate and r$\sb2$ = 0.97 and r$\sb2$ = 0 for 4-(1-adamantyl)-2,6-dimethylphenyl methacrylate copolymers. Reactivity ratios for the copolymer of methyl methacrylate and 4-(1-adamantyl)phenyl methacrylate were r$\sb1$ = 0.59 and r$\sb2$ = 1.92. The three (adamantyl)phenyl methacrylate monomers were incorporated into styrene copolymers at 1-30 mole percent and resulted in T$\rm\sb{g}$ increases of ca 5-60$\sp\circ$C over that of poly(styrene). Incorporation of the monomer into methyl methacrylate copolymers (0.75-35 mol percent) resulted in T$\rm\sb{g}$ increases of ca 6-70$\sp\circ$C over that of poly(methyl methacylate). The second part of this dissertation involves the synthesis of diphenylethynyl-terminated benzoxazoles. 3,5-Diphenylethynylbenzoyl chloride was synthesized by palladium-catalyzed coupling of phenylacetylene with 3,5-dibromobenzoic acid followed by conversion to the acid chloride. 3,5-Diphenylethynylbenzoyl chloride was reacted with 2,2-bis(3-amino-4-hydroxyphenyl)-1,1,1-3,3,3-hexafluoropropane to form a difunctional bisbenzoxazole model compound and used as an end-capper for benzoxazole oligomers. The model compound and oligomers were synthesized in a two-stage reaction in which hydroxyamides were formed first and isolated at room temperature. The hydroxyamides were then thermally cyclized to form the benzoxazole derivatives. The two higher molecular weight benzoxazole oligomers were cast from CHCl$\sb3$ into tough, creasable thin films which showed T$\rm\sb{g}$'s of 137-285$\sp\circ$C. They cured between 320-440$\sp\circ$C to give materials with T$\rm\sb{g}$'s between 300-333$\sp\circ$C. The cured materials showed a 5% weight loss at ca 540$\sp\circ$C in nitrogen and char yields of 55-60%. (Abstract shortened by UMI.)