Siklohekzenoksit'in katyonik polimerizasyonunda tetrametil tiouramdisülfit'in etkisi

Abstract

Bu çalışmada, radikal kaynağı ve elektron transfer bileşiği kullanılarak katyonik ısısal polimerizasyonla fonksiyonel uç gruplu (telechilic) polimer ve bu polimerden de initer sistemle (radikalik polimerizasyon) blok kopolimer sentez edilmiştir. Bu amaçla, radikal kaynağı olarak tetrametiltiouramdisülfit (TMTD) ve elektron transfer bileşiği olarak N-etoksi-2-metil-piridinyum hegzafloro fosfat (EMP) kullamlarak siklohekzenoksit'in (CHO) katyonik polimerizasyonu gerçekleştirilmiştir. Elde edilen polimerin (T-PCHO) tiouram uç grubunun initer özelliğinden faydalanılarak, radikalik polimerleşen bir monomer olan metilmetakrilat varlığında fotokimyasal olarak blok kopolimer sentezi gerçekleştirilmiştir. T-PCHO ve blok kopolimerler ER, UV, GPC kullanılarak karakterize edilmiştir. T-PCHO varlığında MMA'tan fotokimyasal yolla elde edilen polimerlerin, dönüşüm ile molekül ağırlıklarının lineer değişimi, tiouram gubunun varlığını ve initer özellik gösterdiğini kanıtlamaktadır. O s s ^^ ^/ a Me2-N-^-S-S-C-N-Me2 + (Ql *? Me^-N-^-S Ş PF6 l + 6 OEt S ^wwwwwwiwwuw» ^ l^S^ - M - O- S. +. *********************** MMA ~B?_N_£_S. +. Blok kopolimer iv

There have been several classical methods for the preparation of block copolymer which generally involve the successive polymerization of two ör more monomers by the same mechanism. Transformation reactions extend the range of possible monomer combinations in block copolymer. This approach allows to be terminally functionalized by groups capable of initiating a different mode of polymerization The iniferter method, for the preparation of block copolymers, has been extensively explored during the last decade, primarly by Otsu et al. in this concept, iniferters (initiator - transfer agent -terminator) were used to design the structure of polymer chain ends in radical polymerization. Several organic disulfides and phenyl azotriphenylmethane were found to serve asphoto and thermal iniferters,respectively. Polymers obtained by using iniferters,still have iniferter function capable of initiating the polymerization of another monomer yielding block copolymers. İniter (initiator-terminator) compounds have the ability to initiate the polymerization and take part termination reactions. The cationic polymerization of cyclohexeneoxide was studied in the presence of tetramethylthiuram disulfide (TMTD) and N-etoxy-2-methyl-pyridine hexaflouro phosphate (EMP) as radical source and electron transfer agent, respectively. The polymers obtained this way shovved initer functionality as was evidenced by block copolymerization reactions according to the following reaction. O 5 S ^ <^^ S Me2-N-C-S-S-C-N-Me2 + (O^ *. Me2-N-C-S ~~«»~»»~*~»*~>»~» PFe l+ t 6 OEt î MMA u »^^^^ " MMA Mer-N-C-5 - +. ~*~*~~~~~«~~«~»~ Block copolymer v The polymerization of CHO was carried out in the presence of TMTD and EMP. Poly cyclohexeneoxide with thiuram end groups (T-PCHO) was used to initiate the radical photo polymerization of methylmethacrylate (MMA) via initer (initiator-transfer) mechanism. The UV spectrum of T-PCHO possesses an absorbtion band at around X=278 nm region (figure 1) indication attachement of thiuram end groups + 1.09A 0.200 < A/DIU + 0.00A 200.0 50.0<="" ii="" "b="" h="" ö="" es="" an="" _c="" ol="" 's'="" if)="" -="" 2p -t="" no="" pu="" _l="" 1-="" q=""