Abstract
As an important class of reversible deactivation radical polymerization (RDRP), reversible addition fragmentation chain transfer (RAFT) polymerization has attracted great attention attributed to its facile and flexible features to prepare well-defined polymers with different complex structures. In addition, the combination of RAFT with click chemistry provides more effective strategies to fabricate advanced functional materials. In this work, a series of temperature responsive tetra-arm telechelic poly(N-isopropylacrylamide)s (PNIPAs) with propargyl end groups were prepared for the first time through RAFT and subsequent aminolysis/Michael addition modification. The temperature sensitivities of their aqueous solutions were researched via turbidity measurement. It was found that the phase transition temperature of obtained PNIPAs increased with their molecular weights ascribed to their distinctions in the hydrophobic/hydrophilic balance. Subsequently, β-cyclodextrin (β-CD) functionalized with azide moieties was used to crosslink the prepared propargyl-terminated tetra-arm PNIPAs through click chemistry, fabricating corresponding hydrogels with thermoresponse. Similar to their precursors, the hydrogels demonstrated the same dependence of volume phase transition temperature (VPTT) on their molecular weights. In addition, the incorporation of β-CD and the residual groups besides crosslinking may provide a platform for imparting additional functions such as inclusion and adsorption as well as further functionalization.
Highlights
The development of reversible deactivation radical polymerization (RDRP) has opened a series of effective routes to prepare well-defined polymers with various advanced architectures and functionalities
In order to obtain a series of well-defined tetra-arm PNIPAs with different molecular weights via reversible addition fragmentation chain transfer (RAFT) polymerization, a tetra-arm star-chain transfer agents (CTAs) containing a trithiocarbonate moiety at every end was synthesized according to the method described in the literature [12,28]
A series of well-defined tetra-arm telechelic PNIPAs with propargyl terminal groups were synthesized via RAFT polymerization and further modification
Summary
The development of reversible deactivation radical polymerization (RDRP) has opened a series of effective routes to prepare well-defined polymers with various advanced architectures and functionalities. The most frequently applied RDRP techniques include atom transfer radical polymerization (ATRP) [1], nitroxide mediated radical polymerization (NMP) [2], and reversible addition fragmentation chain transfer (RAFT) polymerization [3]. As reviewed in literatures [4,5,6], the utilization of RAFT CTA provides researchers with abundant imagination containing CTA structure design and/or thiocarbonylthio transformation and subsequent thio-chemistry. It is well-known that N-isopropylacrylamide (NIPA) is a typical monomer for synthesizing temperature responsive polymers, and the aqueous solution of NIPA homopolymer has a lower critical
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