Preparation of Amphiphilic Polysilsesquioxane by Grafting of Block Copolymer of Acrylamide Monomers

Abstract

ABSTRACT:The polysilsesquioxane having dithiocarbamate groups was utilized for the graftation of N-isopropylacrylamide (NIPAM) and N,N-dimethylacrylamide (DMAA) under thermal polymerization conditions. The controlled graft polymerization through RAFT process proceeded effectively to give several kinds of block copolymer of NIPAM and DMAA without formation of gel product, in which the sequence and the number of the monomer units were changed. The introduction of the block copolymers provided an amphiphilic property to the polysilsesquioxane. The hydrophilic property, which was shown as solubility in water and contact angle, was affected by the sequence and the number of the monomer units in the graft chain. Furthermore, as the expected property due to a hydrophobic aggregation of NIPAM units, the contact angles of the grafted polysilsesquioxanes measured at 60 C were larger than those at 23 C.[doi:10.1295/polymj.PJ2006126] KEY WORDS Amphiphilic Polysilsesquioxane / N-Isopropylacrylamide / RAFT Process / Graft Polymerization / Recently, various investigations on oligomeric and polymeric silsesquioxanes, which stress on the modifications by various organic functional groups, have been presented from the interests in a useful hybrid material. [1][2][3][4][5][6][7][8][9] As an effective procedure for the modifications of the silsesquioxanes, the graft polymerization from polysiloxane backbone is nominated. [10][11][12][13][14][15][16] This procedure enables to provide the additional functions based on the polymeric components without loosing the essential properties of inorganic polysiloxane backbone such as durability for heat and weatherability. We also have investigated on the graft polymerizations from polysilsesquioxanes, which intended to develop the new multi-functional hybrid materials. [17][18][19] As an example of such graftings, the introduction of copolymer of N,N-dimethylacrylamide (DMAA) and N-isopropylacrylamide (NIPAM) was reported in the previous work. 20 The obtained polysilsesquioxane derivative successfully showed amphiphilicity and thermoresponsive phase separation. The investigations concerning the later property caused by polymerized NIPAM (polyNIPAM) have been widely developed and various applications are proposed such as microencapsulation, biosensor, and drug delivery. [21][22][23][24][25] Such facts support the expectation that the polysilsesquioxane, combined the inorganic polysiloxane backbone with the thermoresponsive and amphiphilic graft chains, will be a candidate for high performance hybrid materials. [26][27][28] Our previous grafting was conducted through free radical polymerization by the use of mercapto groups on the polysilsesquioxane backbone. 20 In the use of the procedure, the graft chain was essentially consisted of the random copolymer of NIPAM with DMAA (polyNIPAM-ran-polyDMAA) and the number of introduced monomer units was limited because of inactivation of radical species during the polymerization. On the other hand, the investigations on such functional polymer are prog...

Preparation of Stimuli-responsive Polysilsesquioxane Grafted Block Copolymer of Acrylamide Monomers

“…[10][11][12][13][14][15][16] In the previous works, we also have investigated concerning the graft polymerizations from polysilsesquioxane backbone, which intended to develop the new multi-functional hybrid materials. [17][18][19][20][21] As an example of such graftings, the introduction of block copolymer of N,N-dimethylacrylamide (DMAA) and N-isopropylacrylamide (NIPAM) by the living polymerization technique, reversible addition-fragmentation chain transfer (RAFT) process, was reported. 21 In the graft polymerization, the PSQ having chloromethylphenyl groups (CPPSQ) was prepared from the corresponding trimethoxysilane and, then, N,N-dimethyldithiocarbamate (DTC) group was introduced as a chain transfer specie for RAFT process.…”

“…[17][18][19][20][21] As an example of such graftings, the introduction of block copolymer of N,N-dimethylacrylamide (DMAA) and N-isopropylacrylamide (NIPAM) by the living polymerization technique, reversible addition-fragmentation chain transfer (RAFT) process, was reported. 21 In the graft polymerization, the PSQ having chloromethylphenyl groups (CPPSQ) was prepared from the corresponding trimethoxysilane and, then, N,N-dimethyldithiocarbamate (DTC) group was introduced as a chain transfer specie for RAFT process.The previous results demonstrated that the block copolymer grafted PSQs showed an expected amphiphilic property, where the solubility in water was influenced by the sequence and number of the monomer units in the grafted chain. 21 Namely, when the more hydrophilic poly(DMAA) was grafted from the polysilsesquioxane backbone at first and poly(NIPAM) was grafted after poly(DMAA) component [poly(DMAA)-blockpoly(NIPAM)], hydrophilic property of the corresponding PSQ was effectively improved.…”

“…21 In the graft polymerization, the PSQ having chloromethylphenyl groups (CPPSQ) was prepared from the corresponding trimethoxysilane and, then, N,N-dimethyldithiocarbamate (DTC) group was introduced as a chain transfer specie for RAFT process.…”

“…As mentioned above, several grafted PSQs obtained in the previous work, which contained the different sequence and the molecular weight of polymeric components, were employed for the evaluation of thermoresponsivility. 21 In addition, several PSQ derivatives, which had organic functional groups besides the graft copolymers, were newly prepared from the expectation to provide a multi-functionality. For the formations of quarternary ammonium salt, triethylamine or N,N-dimethylaniline was treated with chloromethylphenyl group on the PSQ backbone, respectively.…”

“…The preparations of the PSQs having chloromethylphenyl groups (CPPSQ), DTC groups (DTPSQ), and the grafted PSQs containing block and random copolymers of NIPAM and DMAA were reported in the previous work. 21 The PSQs newly prepared in this work were depicted as follows. …”