Introducing small cationic groups into 4-armed PLLA-PEG copolymers leads to preferred micellization over thermo-reversible gelation

POLYMER

卷:54

Article

Wennink, J. W. H.^1,2  Signori, F.^1,2,4  Karperien, M.^1,2  Bronco, S.³  Feijen, J.^1,2  Dijkstra, P. J.^1,2 

[1] Univ Twente, MIRA Inst Biomed Technol & Tech Med, Dept Polymer Chem & Biomat, Fac Sci & Technol, NL-7500 AE Enschede, Netherlands

[2] Univ Twente, MIRA Inst Biomed Technol & Tech Med, Dept Dev Bioengn, Fac Sci & Technol, NL-7500 AE Enschede, Netherlands

[3] CNR, Area Ric Pisa, Ist Proc Chim Fis, CNR IPCF, I-56124 Pisa, Italy

[4] CNR IPCF, INSTM, Area Ric Pisa, I-56124 Pisa, Italy

关键词: Amphiphilic block copolymers;    Micellization;    Hydrogels;   

DOI  :  10.1016/j.polymer.2013.11.007

来源: Elsevier

【 摘 要 】

Starting from bis-MPA, PEG-PLLA triblock copolymers (bis-MPA-(PLLA PEG)2), comprising a central N-hydroxysuccinimide active ester, were synthesized. Reacting the corresponding active ester with alpha,omega-diamines afforded four-armed (PEG-PLLA)(2)-R-(PLLA-PEG)(2) copolymers with central alpha,omega-diamide groups (R). Applying the alpha,omega-diamines, hexamethylene-diamine, spermine or norspermidine none, one or two secondary amine groups, respectively, were introduced into the linking moiety R Whereas a copolymer containing no secondary amine groups showed fully thermo-reversible gelation behavior, copolymers comprising a central moiety containing one or two secondary amine groups retained the 'sol' state after a few heating and cooling cycles. Dynamic light scattering revealed that the copolymer containing no secondary amine groups showed a thermo-reversible shift in micellar size and small aggregates (57 and 877 nm at 25 degrees C and 40 and 152 nm at 50 degrees C). Conversely, copolymers comprising a central moiety containing secondary amine groups show a temperature independent distribution mainly consisting of micelles. It is proposed that the protonated amine groups preferably are located at the corona of the micelles and micellar aggregates and/or shielded by the PEG blocks, hindering the formation of hydrogels by PEG entanglements upon a change in temperature. (C) 2013 Elsevier Ltd. All rights reserved.

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