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Abstract |
A well-defined amphiphilic phenylthiosemicarbazonebased block copolymer was successfully synthesized via reversible addition-ragmentation chain transfer (RAFT) polymerization, followed by postpolymerization modification. Poly(N,N-dimethylacrylamide) (pDMA) was synthesized via RAFT polymerization of N,Ndimethylacrylamide (DMA). The resulting pDMA macrochain transfer agent was further extended using 3-vinylbenzaldehyde (VBA) to yield the poly[(N,N-dimethylacrylamide)-b-(3-vinylbenzaldehyde)] [p- (DMA-b-VBA)] block copolymer. The aldehyde groups of p(DMA-bVBA) were then made to react with 4-phenylthiosemicarbazide to yield the target block copolymer poly {N,N-dimethylacrylamide-b-[N-phenyl2-(3-vinylbenzylidene)hydrazine carbothioamide] } [p(DMA-bPVHC)]. p(DMA-b-PVHC) self-assembled in aqueous solution to yield polymeric micelles that comprise a pDMA block that forms a hydrophilic shell and a pPVHC block that forms a hydrophobic core. p(DMA-b-PVHC) micelles can detect Cu(II) ions which can be determined by a color change from colorless to yellow induced by the formation of coordination complexes between Cu(II) ions and the phenylthiosemicarbazone units of p(DMA-b-PVHC). As Cu(II) ions slowly penetrated the core of p(DMA-b-PVHC) micelles, these cores cross-linked with each other, which in turn resulted in the micelle particles swelling in water. Upon the addition of Cu(II) ions to a solution of p(DMA-b-PVHC) micelles encapsulating the hydrophobic model drug coumarin 102, this drug was released from the micelles in a sustained manner due to the gradual swelling of the cross-linked micelle cores caused by the slow penetration of Cu(II) ions. |
