THERMAL STABILITIES OF HYDROXYALKYL TERMINATED POLYDIMETHYLSILOXANE OLIGOMERS

The thermal stabilities of alpha,omega-hydroxypropyl, alpha,omega-hydr oxybutyl alpha,omega-2-hydroxypentyl and alpha,omega-hydroxyhexyl term inated polydimethylsiloxane oligomers were investigated. Hydroxypropyl and hydroxybutyl terminated polydimethylsiloxane oligomers showed deg radation upon heating through the loss of functional end groups, as de termined by FTIR spectroscopy and gel permeation chromatography. alpha ,omega-Hydroxyhexyl and alpha,omega-2-hydroxypentyl terminated polydim ethylsiloxane oligomers were stable under similar conditions. The inst ability of the end groups is due to the backbiting of the terminal sil icon in the PDMS by the primary hydroxyl oxygen, leading to the format ion of 5- and 6-membered stable, heterocylic compounds. Loss of end gr oups also resulted in a dramatic increase in the molecular weights of the oligomers produced, as determined by GPC.