Poly block copolymer synthesis

Kim KT, Vandermeulen GWM, Winnik MA, Manners I (2005) Organometallic-polypeptide block copolymers synthesis and properties of poly(ferrocenyldimethylsilane)-b-poly (gamma-benzyl-L-glutamate). Macromolecules 38 4958 961... 

While all previous examples employ enzymatic ROP, there are two reports on block copolymer synthesis employing enzymatic poly condensation. The first one was published by Sharma et al. and describes the synthesis and solid-state properties of polyesteramides with poly(dimethylsiloxane) (PDMS) blocks [21]. The polycondensation was carried out with various ratios of dimethyl adipate. 

Block copolymer synthesis using GTP synthesis of poly(methyl methacrylate-fa-n-butyl methacrylate) (Scheme 3)... 

Fig. 5 Schematic representation of the block copolymer synthesis using the example of poly(2-(2-(4-(4-(4-cyano-phenylazo)-phenoxy)-butyric acid)ethyl es ter)et h y I cnc)-block- pol y st y re n e.

HAL Kalacheva, S., Rangelov, S., and Tsvetanov, C., Poly(glycidol)-based analogues to pluronic block copolymers. Synthesis and aqueous solution properties, Macromolecules, 39, 6845, 2006. 

Dubrovina, L. V Ponomareva, M. A. Shirokova, L. V. Storozhuk, I. R Valetskii, R. M. The study of poly(arylatearylenesulfonoxide) block-copolymers synthesis mode influence on their some properties. High-Molecular Compounds. A, 1981, 23(5), 384-388. 

Potentially, there are greater numbers of monomers that are suitable for cationic polymerization than for anionic, but the cationic method is less successful in block copolymer synthesis because, in many systems, the existence of a living carbocationic species is doubtful. Consequently, the involvement of carbocations in block copolymer synthesis tends to be limited to mixed reactions, e.g., the couphng of poly(tetrahydro-furan) cations with polystyryl anions to give an (A - B) diblock (Equation 5.19). 

In the case of AB diblock copolymers prepared by the RAFT technique, the order of monomer addition must be taken into account. A characteristic example of such a block copolymer synthesis is demonstrated in Scheme 19. Initially, a poly(N, N-dimethylacrylamide) (PDMA) macro-CTA was prepared, followed by the use of PDMA-CTA as an initiator to polymerize successfully the second monomer N,N-dimethyl vinyl benzy-lamide (DMVBA). The final diblock copolymer is not contaminated with homopolymer. It has been discovered that the reverse approach is impossible, probably due to the slow fragmentation of the intermediate radical or due to the slow initiation efficiency of the intermediate radical (styrenic macroradical). 

Cammas, S. and Kataoka, K. (1995) Functional poly [(ethylene o.xide)-co-((8-benzyl L-aspartate) ] polymeric micelles block copolymer synthesis and micelles formation. Makromol. Chem. Phys., 196, 1899-1905. 

McGrath and coworkers [217] demonstrated that the use of the dilithium initiator, 90, provides a very versatile method with respect to the ability to vary the chemical composition of the end blocks after first polymerizing a diene such as butadiene or isoprene. The a,to-dilithiumpolydiene center block can be used to initiate the polymerization of polar monomers to form both end blocks simultaneously. This type of triblock copolymer with polar end blocks cannot be prepared by other block copolymer synthesis procedures. Thus, they prepared poly(tert-butyl methacrylate)-btocfc-polyisoprene-Wock-poly(fcrf-butyl methacrylate) triblock copolymers. However, the resulting triblock copolymers did not exhibit well-defined structures. The molecular weight distributions tended to be broad (M /M =1.10-1.25) or bimodal. 

Binder, W.H. and Machl, D. (2005) Poly(ether ketone)-polyisobutylene block copolymers Synthesis and phase behavior. Journal of Polymer Science Part A-Polymer Chemistry, 43,188-202. 

Lin, C.-H., Tung, Y.-C., Ruokolainen, J. et al. (2008) Poly[2,7-(9,9-dihexylfluorene)]-l)/oc -poly(2-vinylpyridine) rod-coil and coil-rod-coil block copolymers Synthesis, morphology and photophysical properties in methanol/THF mixed solvents. Macromolecules, 41,8759-8769. 

Tung, Y.C. and Chen, W.C. (21009) Poly[2,7-(9,9-dihexylfluorene)]-Woc/ -poly[3-(trimethoxysilyl)propyl methacrylate] (PF-b-PTMSPMA) rod-coil block copolymers synthesis, morphology and photophysical properties in mixed solvents. Reactive Functional Polymers, 69,507-518. 

Wang, Y, Zou, S., Kim, K.T. et al. (2008) OrganometaUic-polypeptide block copolymers synthesis and self-assembly of poly(fenocenyldimethylsilane)-b-poly(epsilon-benzyloxycarbonyl-L-Lysine). Chemistry-A European Journal, 14,8624-8631. 

According to the second method of carbonate block copolymer synthesis, sequential monomer polymerization is proceeded with transformation of the active center. The block copolymers are prepared in three steps. First, the polymerization of one monomer is carried out. After complete conversion of the first monomer the transformation of active centers is performed, and the initiation of the polymerization of the second monomer is proceeded. For example, this approach was applied for obtaining poly(styrene-l7-neopentyl carbonate).After completion of the styrene living polymerization, carbanionic centers were transformed into alkoxide ones via reaction with EO and then the ROP of neopentyl carbonate polymerization was performed. In the case of block copolymers of methyl methacrylate with neopentyl carbonate living PMMA, prepared according to GTP, was used as a macroinitiator for DTC polymerization. A silyl keteneacetal active center was transformed to an alkoxide one. Depending on the functionality of the macroinitiator (A) used for cyclic carbonate polymerization, two types of block copolymers can be obtained A-B or B-A-B. 

Another example for block copolymer synthesis is the preparation of poly (methylene-fc-styrene), which was achieved by using a hydroxyl-terminated living polystyrene obtained by TEMPO-mediated living radical polymerization [75] (Scheme 55). The chain end hydroxyl group was transformed into an allyl ether moiety, which was subjected to hydroboration with BH3 to afford polystyrene macroinitiator for the polymerization of 11. After chain elongation with 11 oxi-dation of the C-B chain ends furnished poly(methylene- -styrene) bearing TEMPO and hydroxyl group at chain ends. 

Gilroy JB, Patra SK, Mitchels JM, Winnik MA, Manners I (2011) Main-chain heteaobi-metallic block copolymers synthesis and self-assembly of polyfiarocenylsUane-b-poly (cobaltoceniumethylene). Angew Chem Int Ed 50 5851-5855... 

Starting with a functionaUzation of a,(o-dihydroxy-terminated poly(ethylene oxide) or poly(propylene oxide) by HDl 18, followed by a reaction with a,(0-diamino-terminated copolymer of butadiene and acrylonitrile, a triblock macroactivator was synthesized the anionic polymerization of CL at 140 °C in the presence of this copolymer gave an A-B-C-B-A copolymer [61]. A similar macroactivator for block copolymer synthesis was prepared by a stepwise anionic polymerization of isoprene (with dilithium a-methylstyrene tetramer) and oxirane [62]. 

Enzymatic ROP has also been successfully combined with chemically catalyzed polymerization methods in SCCO2, allowing the formation of block structures. For example, Howdle and coworkers reported a simultaneous use of Novozym 435 with metalblock copolymers of PCL and PMMA [107, 108], whilst a two-step methodology was used to form block copolymers of PCL with poly(fluoro-octyl methacrylates) (PFOMA) [109]. Similar reactions, simultaneously combining reversible addition-fragmentation chain transfer (RAFT) with enzymatic ROP to form block copolymers of polystyrene and PCL, have also been performed in SCCO2 [110]. Block copolymer synthesis in SCCO2 has recently been reviewed [111]. 

Polymerization ofiVIasked Disilenes. A novel approach, namely, the anionic polymerization of masked disilenes, has been used to synthesize a number of poly(dialkylsilanes) as well as the first dialkylamino substituted polysilanes (eq. 13) (111,112). The route is capable of providing monodisperse polymers with relatively high molecular weight M = lO" — 10 ), and holds promise of being a good method for the synthesis of alternating and block copolymers. 

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