Block copolymers derived from 2,2′-azobis(2-cyanopropanol). I. Synthesis of poly(urethane-block-methyl methacrylate) and poly(urethane-block-styrene)

✍ Scribed by Talal Cheikhalard; Valerie Massardier; Lan Tighzert; Jean Pierre Pascault

• Publisher: John Wiley and Sons
• Year: 1998
• Tongue: English
• Weight: 247 KB
• Volume: 70
• Category: Article
• ISSN: 0021-8995
• DOI: 10.1002/(sici)1097-4628(19981017)70:3<613::aid-app24>3.0.co;2-#

✦ Synopsis

Block copolymers with polyester-urethane and polymethyl methacrylate (PMMA) or polystyrene (PS) sequences were obtained by the use of polyester-or polyether-urethane macroazo initiators (PUMAI). PUMAI with a well-defined number of azo groups per chain were prepared via a two-stage reaction procedure using 2,2Ј-azobis(2-cyanopropanol) (ACP), 4,4Ј-methylene diphenyl diisocyanate (MDI) and ␣, -hydroxy polycaprolactone (PCL). The characteristics of the obtained block copolymers depend on the reaction conditions, and a yield of 98% was obtained for a P(U-b-MMA) synthesized with a ratio of macroazo initiator to monomer equal to 1/400. In similar conditions, copolymerization of styrene was more difficult, and the maximum block copolymer yield obtained in this work was only of 37% for a ratio of macroazo initiator to monomer equal to 1/150. Combination of different analyses Fourier transform infrared (FTIR) spectroscopy, proton nuclear magnetic resonance ( 1 H-NMR), and size exclusion chromatography (SEC) carried out on both crude and fractionated copolymers showed this kind of synthesis yielding di-and triblock copolymers and only a little amount of PU homopolymer.