SYNTHESIS AND CHARACTERIZATION OF A POLYPHENYLACETYLENE WITH DENDRON PENDANTS

Polymerization of a phenylacetylene monomer bearing a dendron moiety was carried out by using a rhodium complex Rh[(nbd)Cl₂]₂ as catalyst. The structure of the resultant was characterized with infrared (IR), nuclear magnetic resonance ( NMR ) , and UV-Visible absorption spectroscopic techniques ; the experimental data confirmed the generation of the expected polyphenylacetylene derivative (P1) with dendron pendants. P1 was soluble in common organic solvents such as chloroform, N, N-dimethylformamide oxide,and tetrahydrofurran (THF) , and its average molecular weight was about 57300. The steric repulsion of between the bulky dendritic side chains make the polymer main-chain take a stereoregular cis-cisoid conformation. Consequently, P1 exhibits a pronounced shoulder at around 440 nm in the absorption spectrum its THF solution. Meanwhile, the bulky dendrons around the polymer main-chain protect the main-chain from thermal-induced decomposition via the "jacket effect", thus P1 lost 5% of its weight at a temperature of 295°C ,which is about 70°C higher than its parent polymer, or polyphenylacetylene.