Synthesis of polydimethylsiloxane-block polystyrene-b/ock-polydimethylsiloxane via polysiloxane-based macroinitiator in supercritical CO2

• Published in: Polymer international Vol. 54; no. 2; pp. 374 - 380
• Main Authors: Akgun, Mesut, Deniz, Sennur, Baran, Nil, Uzun, Nimet I, Akgun, Nalan A, Dincer, Salih
• Format: Journal Article
• Language: English
• Published: 01-02-2005
• ISSN: 0959-8103; 1097-0126
• DOI: 10.1002/pi.1695

Polydimethylsiloxane-block-polystyrene-block-polydimethylsiloxane (PDMS-b-PS-b-PDMS) was synthesized by the radical polymerization of styrene using a polydimethylsiloxane-based macroazoinitiator (PDMS MAI) in supercritical CO2. PDMS MAI was synthesized by reacting hydroxyterminated PDMS and 4,4'-azobis(4-cyanopentanoyl chloride) (ACPC) having a thermodegradable azo-linkage at room temperature. The polymerization of styrene initiated by PDMS MAI was investigated in a batch system using supercritical CO2 as the reaction medium. PDMS MAI was found to behave as a polyazoinitiator for radical block copolymerization of styrene, but not as a surfactant. The response surface methodology was used to design the experiments. The parameters used were pressure, temperature, PDMS MAI concentration and reaction time. These parameters were investigated at three levels (-1, 0 and 1). The dependent variable was taken as the polymerization yield of styrene. PDMS MAI and PDMS-b-PSb-PDMS copolymers obtained were characterized by proton nuclear magnetic resonance and infrared spectroscopy. The number- and weight-average molecular weights of block copolymers were determined by gel permeation chromatography.