PREPARATION AND CHARACTERIZATION OF BLOCK AND GRAFT-COPOLYMERS USING MACROAZOINITIATORS HAVING SILOXANE UNITS

alpha,omega-Amine terminated organofunctional polydimethylsiloxane (PD MS) was condensed with 4,4'-azobis-4-cyanopentanoyl chloride (ACPC) to prepare macroazoinitiators containing siloxane units. Interfacial pol ycondensation reaction at room temperature was applied: ACPC was sligh tly dissolved in carbon tetrachloride and it was poured on aqueous NaO H solution of PDMS. Block copolymers containing PDMS as a block segmen t combined with polystyrene (PS) have been derived by the polymerizati on of styrene monomer initiated by these macroazoinitiators. PS-b-PDMS block copolymers were characterized by using nuclear magnetic resonan ce and infrared spectroscopy. Thermal and mechanical properties of the block copolymers were studied by using thermogravimetric analysis, di fferential scanning calorimetry, and a Tensilon stress-strain instrume nt. The morphology of block copolymers was investigated by scanning el ectron microscopy. PDMS-g-polybutadiene (PBd) graft copolymers were al so prepared by reaction of PBd with the above macroazoinitiator. Incre ase in the amount of macroazoinitiator in the mixture of PBd (52% w/w) leads to the formation of crosslinked graft copolymers. Molecular wei ghts of soluble graft copolymer samples were between 450 and 600 K wit h a polydispersity of 2.0-2.3. (C) 1996 John Wiley & Sons, Inc.