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...

The polysilsesquioxanes (PSQs) having the graft block copolymer of N-isopropylacrylamide (NIPAM) and N,Ndimethylacrylamide (DMAA), which showed the different sequence and number of the monomer units, were obtained by RAFT process. In addition, the PSQ derivatives containing other organic functional groups besides the grafted polymers were prepared by the use of chloromethylphenyl groups on the starting PSQ. Through the formation of ester bond and quarternary ammonium salt, phenol, triethylamine, and N,N-dimethylaniline groups were introduced into the grafted PSQ, respectively. In the behaviors of reversible thermoresponsive aggregation caused by poly(NIPAM) component, the almost same Lowest Critical Solution Temperature such as 34 C was observed for the grafted PSQs, although the poly(DMAA), phenol groups, and/or the quarternary ammonium salts were existed on the same PSQ backbone. As an additional function, the presence of phenol groups led to pH responsive solubility in water. The solubility of the PSQs in water was also affected by hydrophilic property of the amines to form the quarternary ammonium salts. In addition, a kind of chromism, which related with pH value, was observed in the case containing N,N-dimethylaniline moieties.KEY WORDS: Thermoresponsive Phase Separation / Polysilsesquioxane / N-Isopropylacrylamide / Chromism / 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] The graft polymerization from polysilsesquioxane backbone is shown as an effective procedure for the modifications. The methodology enables to provide the additional functions based on the polymeric components without loosing the essential properties of inorganic siloxane structure such as durability for heat and weatherability. [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.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(...

(3-Mercaptopropyl)trimethoxysilane was employed as a chain transfer for the polymerization of N-isopropylacrylamide (NIPAM) and N,N-dimethylacrylamide (DMAA) under UV irradiation to obtain the corresponding polymers having methoxysilyl end group. By the condensation reaction of such macrosilane coupling reagents under basic or acidic conditions, the grafted polysilsesquioxanes, which were soluble in usual organic solvents, were formed without gelation. The cocondensation of the macrosilane coupling reagents enabled the preparation of the grafted polysilsesquioxane, in which poly(NIPAM) and poly(DMAA) were introduced respectively into the polysilsesquioxane main chain. Such macrosilane coupling reagents and the grafted polysilsesquioxanes showed an amphiphilic property. Furthermore, those containing poly(NIPAM) showed reversible thermoresponsive aggregation in an aqueous solution. In the thermoresponsive phase separation measured by turbidity, no change of aggregation temperature caused by the presence of poly(DMAA) was observed.

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