Synthesis of hydroxyphenylglycine-derived novel poly(silylenevinylenephenyleneethynylene)s

Abstract The hydrosilylation polymerization of d -(−)- p -hydroxyphenylglycine-derived diethynyl monomers 1 p and 1 m with dihydrosilanes Si1 and Si2 was carried out using RhI(PPh 3 ) 3 as a catalyst to give optically active novel poly(silylenevinylenephenyleneethynylene)s [( E )-poly( 1 p - Si1 ), ( E )-poly( 1 p - Si2 ), ( E )-poly( 1 m - Si1 ), ( E )-poly( 1 m - Si2 ), and ( Z )-poly( 1 p - Si1 )] with number-average molecular weights ranging from 2800 to 17,000 in 41–92% yields. Polymers having ( E )- and ( Z )-olefin moieties were obtained, wherein the ( E )-/( Z )-ratios depended on the reaction conditions. The UV–vis absorption edge of ( E )-poly( 1 p - Si1 ) was positioned at a wavelength longer than that of ( Z )-poly( 1 p - Si1 ), indicating that ( E )-vinylene-linkage extends the conjugation more largely than the ( Z )-counterpart. This was also confirmed by fluorescence spectroscopy. Alkaline hydrolysis of ester moieties of these polymers gave the corresponding polymers having carboxy groups. The ( E )-polymers showed different solubility in hydrophobic solvents before and after hydrolysis, but the non-hydrolyzed and hydrolyzed ( Z )-polymers exhibited the same solubility.