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

Abstract

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(...

Thermoresponsive polysilsesquioxane grafted methacrylate polymer with a methoxyethylamide group

“…In the IR spectrum of DTPSQ, a weak absorption due to the hydroxyl group was observed. 27 In our previous investigation on the formation of PSQ with phenyl groups under similar basic conditions, the 29 Si NMR spectrum showed the signals assigned to both the T 2 and T 3 structures. 39 Therefore, the structure of the polysiloxane main chain of DTPSQ was thought to consist of incomplete ladder and cage structures, but not to be randomly cross-linked.…”

“…DTPSQ was prepared according to the procedure reported previously. 27 The estimated values of M n and M w /M n from GPC measurements were 5300 and 1.23, respectively. The dimethyldithiocarbamate group content in DTPSQ was 3.05 mmol eq g -1 .…”

“…[22][23][24][25][26] Our previous efforts, in which a polymer of N-isopropylacrylamide (NIPAM) was chosen and introduced as the graft chain into PSQ backbone, focused on thermoresponsive properties and were also examples of modified hybrids. [27][28] In the graftings from PSQ, one of the findings in the grafting of poly(NIPAM) was that at least 20 monomer units of NIPAM in a graft chain were necessary to maintain a good solubility in water. Consequently, the copolymerization of NIPAM with N,N-dimethylacrylamide was required when a small number of NIPAM monomer units in one graft chain were grafted.…”

“…The photoiniferter technique was applied to the syntheses of thermoresponsive PSQs through graft polymerization of MEMMA, in which the PSQ with a dimethyldithiocarbamate group (DTPSQ) was used. 27,35 In addition, copolymerizations of MEMMA with 2-hydroxyethyl methacrylate (HEMA) were conducted to introduce hydroxyl groups in the polymeric components. Such additional functional groups may be useful when optical and medical uses of the resulting materials are considered.…”

Graft polymerization of acrylamide monomers from polysilsesquioxane containing xanthate groups

“…With the regard to this expectation, we also tried to develop new multifunctional hybrid materials using acrylamide monomers by the graft polymerizations from polysilsesquioxane (PSQ). [21][22][23][24][25][26] In fact, the graftings of polymeric N,N-dimethylacrylamide (DMAA) and N-isopropylacrylamide (NIPAM) successfully produced amphiphilic and thermoresponsive PSQs. 23,24 For the graft polymerizations, the reversible addition-fragmentation chain transfer (RAFT) process was utilized, in which the N,Ndimethyldithiocarbamate (DTC) group was chosen as the chain transfer species.…”