BACKGROUND: ABA‐type poly(methyl methacrylate) (PMMA) and fluorine‐containing polyimide triblock copolymers are potentially beneficial for electric materials. In the work reported here, triblock copolymers with various block lengths were prepared from fluorine‐containing difunctional polyimide macroinitiators and methyl methacrylate monomer through atom‐transfer radical polymerization. The effects of structure on their solid and thermal properties were studied. RESULTS: The weight ratios of the triblock copolymers derived using thermogravimetric analysis were shown to be almost identical to the ratios determined using 1H NMR. The solid properties (film density and maximum d‐spacing value) and thermal properties (glass transition and thermal expansion) were shown to be strongly dependent on the weight ratios of both PMMA and polyimide components. Furthermore, a porous film, which showed a lower dielectric constant of 2.48 at 1 MHz, could be prepared by heating a triblock copolymer film to induce the thermal degradation of the PMMA component. CONCLUSION: The use of the polyimide macroinitiator was useful in the preparation of ABA‐type triblock copolymers to control each block length that influences the solid and thermal properties. Additionally, the triblock copolymers have great potential in preparing porous polyimides in the application of electric materials as interlayer insulation membranes of large‐scale integration. Copyright © 2009 Society of Chemical Industry

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...

Polysilsesquioxane with phenyl and chloromethylphenyl groups (PCPSQ) was prepared readily from phenyltrimethoxysilane and [2‐(chloromethylphenyl)ethyl]trimethoxysilane under acidic conditions. Polymerization with chloromethylphenyl groups on PCPSQ with methyl methacrylate (MMA) was conducted in the presence of a catalytic amount of copper(I) bromide and (−)‐sparteine. Atom transfer radical polymerization yielded a graft polymer (PCPSQ‐g‐MMA) efficiently, and no gelation was observed. The process was also applied to the preparation of graft block copolymers on PCPSQ with several methacrylate monomers. An advantage of the graft hybrid polymers was shown in improved thermal behavior. © 2004 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 42: 4212–4221, 2004

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