Preparation of crosslinked and graft copolymers via photoinitiated polymerization

Abstract

Block and graft copolymers are the most demanded advanced materials since they display combined physical and mechanical properties. Because of their diverse macromolecular structures, they may possess novel characteristics required for many high-lech applications. Preparation of block-graft copolymers is described using a side-chain N,N-dimethylamino functional precursor polymer. Since the functional sites for grafting are placed in each repeating unit of a segment, the resulting polymer is a brush type block-graft copolymer. For this purpose, monodisperse poly(N,N-dimelhyl-4-vinylphenethylamine-block-styrene), [P(PTA-b-St)] block copolymer was synthesized by sequential addition of N,N-dimethyl-4-vinylphenethylamine (PTA) and styrene (St) by anionic living polymerization, carried out at —78°C under a pressure of $10^{-6}$ torr using cumyl potassium as the initiator. The diblock copolymer containing N,N-dimethyl amino groups in one segment was used as a backbone in the photografting experiments for the preparation of polymer brushes by the 'grafting from' strategy. Photoinduced radical polymerization of styrene through side chain-functional N,N-dimethyl amino groups yielded both crosslinked polymer and a brush type block-graft copolymer to a lesser extent. Upon irradiation at a wavelength of 350 nm, macroradicals were generated via hydrogen abstraction from amino side-chain groups by the excited benzophenone. The carbon centered radicals, thus generated, initiated the free radical polymerization of methylmelhacrylate (MMA). Formation of block-graft copolymer was evidenced by GPC and H-NMR analyses.

Özet

Yan zincir fonksiyonlu önpolimer kullanılarak fırça tipli blok-aşı kopolimer eldesi incelendi. İlk olarak, kümil potasyum başlatıcısı varlığında, —78'C'de ve $10^{-6}$ torr basınç altında gerçekleştirilen anyonikyasayan polimerizasyonla düşük molekül ağırlığı dağılımlı poli(N,N-dimetil-4-vinilfenetilamin)-blok-polistiren sentezlendi. Daha sonra, N,N-dimetil amino yan zincir fonksiyonlu bu polimerden metil metakrilatın fotokimyasal radikal polimerizasyonu sonucu çapraz bağlı polimer ve daha az oranda fırça tipli blok-aşı kopolimer elde edildi. 350 nm dalgaboylu ışıkla uyarılan benzofenonun yan zincirdeki amino gruplarından hidrojen koparmasıyla makroradikal oluşumu sağlanmıştır. Blok-aşı kopolimerin karakterizasyonu H-NMR, ve GPC analizleriyle yapıldı.