Pentablock copolymers

Brzezinska KR, Curtin SA, Deming TJ (2002) Polypeptide end-capping using functionalized isocyanates preparation of pentablock copolymers. Macromolecules 35 2970-2976... 

Figure 7.55. Reaction scheme for the room-temperature synthesis of a CBABC pentablock copolymer, and GPC traces of a,z-dibromo-terminated polystyrene (A, dotted line), poly(fBA-fe-styrene-fe-fBA) (BAB triblock copolymer macroinitiator, dashed line), and poly(MMA-fe-fBA-fe-styrene-fe-f BA-fe-MMA) (CBABC, solid line). The GPC data shows evidence of a successful polymerization route - low polydis-persity index (PDI), and good control over the number-average molecular weight (Mn). Reproduced with permission from Ramakrishnan, A. Dhamodharan, R. Macromolecules 2003, 36, 1039. Copyright 2003 American Chemical Society.

Figure 12.11 Synthesis of the pentablock copolymer PSt-fo-PCL-fo-PEG-fo-PCL-b-PSt by enzymatic ROP and ATRP and AFM height image (a), and cross-sectional analysis (b) of the nanoscale aggregates of the block...

Gao, R., Wang, D., Heflin, J.R., Long, T.E., 2012. ImidazoUum sulfonate-containing pentablock copolymer-ionic liquid membranes for electroactive actuators. J. Mater. Chem. 22,13473-13476. 

Determan, M.D., Cox, J.P. and MaUapragada, S.K., 2007. Drug release from pH-responsive thermogeUing pentablock copolymers. Journal of Biomedical Materials Research Part A, 81A(2), 326-333. 

In a more recent study [88], the chlorine end groups of PIB were quantitatively converted to bromoester groups to facilitate ATRP from end-positioned activated ester groups (Scheme 11.21). In this way, the capping with short blocks of PSt observed in the earlier method could be avoided. The concept was further extended to the preparation of PIB-h-PMMA diblock [89], poly(t-butyl acrylate)-b-polyisobutylene-b-polystyrene triblock [90], and amphiphilic pentablock copolymers based on PIB [91]. 

B. C. Anderson, S. M. Cox, P. D. Bloom, V. V. Sheares, S. K. MaUapragada, Synthesis and characterization of diblock and gel-forming pentablock copolymers of tertiary amine methacrylates, poly(ethylene glycol), and poly(propylene glycol). Macromolecules, 36,1670-1676 (2003). 

Pavlovic, D. Linhardt, J. G. Kunzler, J. F. Shipp, D. A., Synthesis and Characterization of PDMS-, PVP, and PS-Containing ABCBA Pentablock Copolymers. Macromol. Chem. Phys. 2010, 211,1482-1487. 

R. F. Storey, A. D. Scheuer, B. C. Achord, Amphiphilic poly(acrylic add-b-styrene-b-isobutylene-b-styrene-b-acrylic add) pentablock copolymers from a combination of quasiliving carbocationic and atom transfer radical polymerization. Polymer 200S. 46, 2141-2152. 

Amphiphilic block copolymers with covalentiy linked hydrophilic and hydrophobic blocks capable of forming micelles can be conveniently prepared by ATRP techniques [86-88]. A representative example is the synthesis of polymethacrylate based pentablock copolymers (PBPs) via consecutive ATRP technique reported by Xu et al. [89] for non-viral gene delivery applications. In their approach, PBPs of poly(HEMA)-Z7-poly(DMAEMA)-fc-PEG-fc-poly(DMAEMA)-fo-poly(HEMA) were prepared via consecutive ATRPs from di-2-bromoisobutyryl-terminated PEG (Br-PEG-Br) (Fig. 2.24). The very low in vitro cytotoxicity and excellent gene transfer efficacies exhibited by these PBPs demonstrated the versatility of the ATRP technique to tailor the polymer structural-property characteristics for such applications. 

Fig. 2.24 Schematic diagram illustrating the preparation of P(HEMA)-fe-P(DMAEMA)-fc-PEG-f>-P(DMAEMA)-i>-P(HEMA) pentablock copolymer (PBP) via consecutive ATRPs from di-2-bromoisobut5uyl-terminated PEG (Br-PEG-Br) (EG = ethylene glycol, DMAEMA = (2-dimethyl amino)ethyl methacrylate, HEMA = 2-hydroxyethyl methacrylate). Reproduced with permission from Ref. [89] Elsevier...

Xu, F.-J., et al. 2008. Pentablock copolymers of poly(ethylene glyeol), poly((2-dimethyl amino)ethyl methacrylate) and poly(2-hydroxyethyl methacrylate) from consecutive atom transfer radical polymerizations for non-viral gene delivery. Biomaterials 29(20) 3023-3033. 

Outline a simple ATRP strategy with minimum number of steps for the synthesis of ABCBA pentablock copolymers, where A = poly(methyl acrylate), B = poly(tert-butyl acrylate), and C = polystyrene. How would you modify the procedure if A is poly(methylmethacrylate) ... 

Agarwal, A., Unfer, R. and Mallapragada, S.K. (2005) Novel cationic pentablock copolymer as non-viral vectors for gene therapy. /. Control Rekase, 103,245-258. 

NIE Nie, H., Li, M., Bansil, R., Konak, C., HelmstedL M., and Lai, L, Structure and dynamics of a pentablock copolymer of polystyrene-polybutadiene in a butadiene-selective solvent, Polymer, 45, 8791, 2004. 

Only one membrane conformation is possible for AB copolymers, where the B blocks constitute the hydrophobic layer and the A blocks extend outwards on both sides of the membrane. In the case of the ABA triblocks, the hydrophobic B block either can form a loop so as the hydrophilic A chains are on the same side of the membrane (U shape) or can stretch forming a monolayer with the two A blocks at the opposite sides of the membrane (I shape), while for the BAB type only, the U-shaped conformation is possible since the hydrophobic B chain ends must assemble into a membrane and the hydrophilic A blocks must form a loop. Similar conformations can be anticipated for ABABA pentablock copolymers. The same general rules apply when a third chemically different block is added, and although the overall geometry is the same, multiblock copolymers have an extra level of control over the polymersome structure introduced by the extra interaction between the blocks. Hence, ABC triblock copolymers assemble into asymmetric or Janus membranes, and the resulting vesicles are characterised by different external and internal surface chemical properties. Even more interestingly, ABCA tetrablocks (where A is hydrophilic and B and C are both hydrophobic) have been shown to... 

Fujiwara N, Asaka K, Nishimura Y et al (2000) Preparation of gold — solid polymer electrolyte composites as electric stimuli-responsive materials. Chem Mater 12(6) 1750-1754 Fukushima T, Asaka K, Kosaka A et al (2005) Fully plastic actuator through layer-by-layer casting with ionic-liquid-based bucky gel. Angew Chem hit Ed 44 2410-2413 Gao R, Wang D, Heflin JR et al (2012) Imidazolium sulfonate-containing pentablock copolymer-ionic liquid membranes for electroactive actuators. J Mater Chem 22 13473-13476 Gogotsi Y, Nikitin A, Ye H et al (2003) Nanoporous carbide-derived carbon with tunable pore size. Nat Mater 2(9) 591-594... 

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