Synthesis and tunable thermoresponsive solution morphologies of 2, 2‐bis‐methylolpropionic acid dendron–azobenzene–poly(N‐isopropyl acrylamide) copolymers. Issue 7 (6th April 2017)

• Record Type: Journal Article
• Authors: Kalva, Nagendra; Ambade, Ashootosh V
• Is Part Of: Polymer international. Volume 66:Issue 7(2017:Jul.)
• Page Start: 1084
• Page End: 1093
• Publication Date: 2017-04-06
• Subjects: stimuli‐responsive -- block copolymers -- self‐assembly -- click chemistry -- PNIPAM; Plastics -- Periodicals; Polymers -- Periodicals; Polymerization -- Periodicals; 547.7
• DOI: 10.1002/pi.5363
• Languages: English
• ISSNs: 0959-8103

Abstract

Abstract: Amphiphilic temperature‐ and photoresponsive linear–dendritic block copolymers comprising second‐generation acetonide‐2, 2‐bis‐methylolpropionic acid‐based polyester dendron and linear poly( N ‐isopropyl acrylamide) (PNIPAM) linked by an azobenzene unit were synthesized using atom transfer radical polymerization (ATRP) followed by click chemistry. Linear PNIPAM precursor was prepared from an azide‐functionalized azobenzene containing ATRP initiator. Two polymers obtained by varying the chain length of the PNIPAM block showed different morphologies and lower critical solution temperature (LCST) values in aqueous solution. Complete change in morphology of the two polymers into large spherical aggregates and nanotubes, respectively, was observed upon heating the micellar solution above LCST. The azobenzene unit was found to undergo trans – cis photoisomerization in the assemblies and caused a change in the microenvironment of an encapsulated hydrophobic dye without any release. Acetonide groups on the dendron were deprotected to afford hydroxylated polymer that showed well‐defined morphologies above the LCST and after heating–cooling cycle while significant dye encapsulation was seen only above the LCST. © 2017 Society of Chemical Industry Abstract : Linear–dendritic copolymers comprising 2, 2‐bis‐methylolpropionic acid‐based dendron and poly( N ‐isopropyl acrylamide) (PNIPAM) connected through azobenzene were synthesized using click chemistry and atom transfer radical polymerization. PNIPAM chain length and dendron periphery influenced morphology below and above lower critical solution temperature (LCST).