Y-shaped copolymer

Fig. 2.12 A TEM micrograph from an PI2PS Y-shaped copolymer with /PS = 0.17, Mw = 100 kg mol 1 oriented by compression showing (a) four-fold symmetry due to a [100] projection and (b) three-fold hexagonal symmetry due to a (111) projection of the cubic array (Pochan et at. 1996b).

Sun J, Chen X, Guo J, Shi Q, Xie Z, Jing X (2009) Synthesis and self-assembly of a novel Y-shaped copolymer with a helical polypeptide atm. Polymer 50 455-461... 

As discussed in Fig. 8.38, an in situ-formed inverse-Y shaped copolymer is hardly pulled out of the matrix. However, pull-out into the dispersed particles (pull-in) takes place in reactive blending by the use of an extremely long (L/D = 100, L screw length, D screw diameter) twin screw extruder (Sato et al. 2007). Under the intensive shear fields in the extruder, the dispersed particles can be highly deformed, as shown in Fig. 8.40. The deformation to ellipsoids and the recovery to spherical particles would be repeated in the extruder, which implies that, from the shear fields in the dispersed particles, the in sim-formed graft copolymers would pull into the dispersed particles. 

Figure 4.10 Synthesis of Y-shaped copolymer PLLA2-i-PBLG...

A series of Y-shaped amphiphilic PEG(PTMC)2 block copolymers were obtained via ROP of TMC using this mPEG with bishydroxyl end-groups as macroinitiator and ZnEt2 as a catalyst. It was shown that the Y-shaped copolymer mPEG(PTMC)2 could self-assemble into micelles in aqueous medium and the critical micelle concentration values of the micelles decreased with an increase in the hydrophobic PTMC block length of mPEG(PTMC)2. 

Zhulina E., and Balazs A. C., Designing patterned surfaces by grafting Y-shaped copolymers . Macromolecules, 1996 29(7) 2667-2673. 

During the last 5 years, there have been several reports of multiblock copolymer brushes by the grafting-from method. The most common substrates are gold and silicon oxide layers but there have been reports of diblock brush formation on clay surfaces [37] and silicon-hydride surfaces [38]. Most of the newer reports have utilized ATRP [34,38-43] but there have been a couple of reports that utilized anionic polymerization [44, 45]. Zhao and co-workers [21,22] have used a combination of ATRP and nitroxide-mediated polymerization to prepare mixed poly(methyl methacrylate) (PMMA)Zpolystyrene (PS) brushes from a difunctional initiator. These Y-shaped brushes could be considered block copolymers that are surface immobilized at the block junction. 

A series of interesting block copolymer architectures has also been prepared by Zhang et al. In a first paper, the synthesis of H-shaped triblock copolymers was demonstrated from enzymatically obtained PCL diol after end-functionalization with a difunctional ATRP initiator [40]. This allowed the growth of two PS chains from each end of the telechelic PCL. When methanol instead of glycol was used as the initiator in the initial enzymatic CL polymerization, a PCL with one hydroxyl endgroup was obtained. Functionalization of this endgroup with the difunctional ATRP initiator and subsequent ATRP of styrene or GMA resulted in Y-shaped polymers (Scheme 3) [41, 42]. 

Y. Kodera, R. Tanaka, A. Matsushima, and Y. Inada. Chemical modification of 1-asparaginase with a comb-shaped copolymer of polyethylene glycol and maleic anhydride. Btcckem. Biaphys. Res. Comnun. 1S4 144 (1992). 

Cai, Y Armes, S. P. Synthesis of well-defined Y-shaped zwitterionic block copolymers via atom-transfer radical polymerization. Macromolecules 2005, 38, 271-279. 

Xu, F.J. Ping, Y Ma, J. Tang, G.P. Yang, W.T. Li, J. Kang, E.T. Neoh, K.G. Comb-shaped copolymers composed of hydroxypropyl cellulose backbones and cationic poly((2-dimethyl amino) ethyl methacrylate) side chains for gene deHveiy. Bioconjug. Chem. 2009, 20 (8), 1449-1458. 

D.S. Kim, Y.S. Kim, M.D. Guiver, J. Ding, B.S. Pivovar, Highly fluorinated comb-shaped copolymer as proton exchange membranes (PEMs) Fuel cell performance. Journal of Power Sources 2008, 182(1), 100-105. 

As a consequence of this work, a general strategy for the synthesis of reversibly stimuh-responsive Y-shaped polymer bmshes and their surface attachment has been developed (Fig. 60) [237c]. The preparation of the respective junction-point reactive block copolymers relies on a combination of carbanionic and oxyanionic... 

Kagami Y, Gong JP, Osada Y. Shape memory behaviors of crosslinked copolymers containing stearyl acrylate. Macromol Rapid Commun 1996 17(8) 539—43. 

Y-shaped double-hydrophilic block copolymers, with a poly(EO-co-PO) sequence and two blocks of various hydrophilic methacryKc polymers, were synthesized by an elaborated ATRP technique by Armes and co-workers [239]. pH and thermal stimulus-responsive micelles could be obtained by these authors. 

Cay, Y. and Armes, S.P. (2004) Synthesis of novel Y-shaped pH-responsives block copolymers based on poly(alkylene oxides). ACS Polym. Prepr. (Div. Polym. Chem.), 45( 1), 766-767. 

Fujimoto, T., Zhang, H., Kazama, T., Isono, Y., Hasegawa, H. and Hashimoto, T. (1992) Preparation and characterization of novel star-shaped copolymers having 3 different branches. PoZymer, 33,2208-2213. 

Rao, J., Zhang, Y., Zhang, J., Lin, S. (2008). Facile preparation of well-defined AB2 Y-shaped Miktoarm star polypeptide copolymer via the combination of ring-opening polymerization and chck chemistry. Biomacromolecules, 9, 2586-2593. 

Xu, F. J., Zhong, S. P, Yung, L. Y, Tong, Y. W., Kang, E. T., Neoh, K. G. (2006). Thermore-sponsive comb-shaped copolymer-Si(lOO) hybrids for accelerated temperature-dependent cell detachment. Biomaterials, 27,1236-1245. 

Zhang,H.,Yan,Q.,Kang,Y.,Zhou,L.,Zhou,H.,Yuan,J. and Wu,S. (2012). Fabrication of thermo-responsive hydrogels from star-shaped copolymer with a biocompatible j3-cyclodextrin core. Polymer, 53,3719-3725. 

Figure 19.23 Schematic diagrams of linear, Y-shaped, and comb-like rod-coil block copolymer brushes. (Reproduced with permission from C.-S. Li, W.-C. Wu, Y.-J. Sheng and W.-C. Chen Effects of chain architectures on the surface structures of conjugated rod-coil block copolymer, Journal of Chemical Physics, 128, 154908, 2008. 2008 American Institute of Physics.)...

An AB2 Y-shaped polypeptide copolymer was synthesized by click chemistry. A-aminoethyl-3,5-(bisprogargyloxy)benzamide was used as initiator for A-benzyloxycarbonyl-L-lysine (ZLL)-NCA and 3-azido propylamine for BLG-NCA [121]. After deprotection, the block copolymer forms micelles in water with a PLL core at pH = 12 and with a PGA core at pH = 2. 

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