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Title: Role of chain architecture in the solution phase assembly and thermoreversibility of aqueous PNIPAM/silyl methacrylate copolymers
Stimuli-responsive polymers functionalized with reactive inorganic groups enable creation of macromolecular structures such as hydrogels, micelles, and coatings that demonstrate smart behavior. Prior studies using poly( N -isopropyl acrylamide- co -3-(trimethoxysilyl)propyl methacrylate) (P(NIPAM- co -TMA)) have stabilized micelles and produced functional nanoscale coatings; however, such systems show limited responsiveness over multiple thermal cycles. Here, polymer architecture and TMA content are connected to the aqueous self-assembly, optical response, and thermoreversibility of two distinct types of PNIPAM/TMA copolymers: random P(NIPAM- co -TMA), and a ‘blocky-functionalized’ copolymer where TMA is localized to one portion of the chain, P(NIPAM- b -NIPAM- co -TMA). Aqueous solution behavior characterized via cloud point testing (CPT), dynamic light scattering (DLS), and variable-temperature nuclear magnetic resonance spectroscopy (NMR) demonstrates that thermoresponsiveness and thermoreversibility over multiple cycles is a strong function of polymer configuration and TMA content. Despite low TMA content (≤2 mol%), blocky-functionalized copolymers assemble into small, well-ordered structures above the cloud point that lead to distinct transmittance behaviors and stimuli-responsiveness over multiple cycles. Conversely, random copolymers form disordered aggregates at elevated temperatures, and only exhibit thermoreversibility at negligible TMA fractions (0.5 mol%); higher TMA content leads to irreversible structure formation. This understanding of the architectural and assembly effects on the thermal cyclability of aqueous PNIPAM- co -TMA can be used to improve the scalability of responsive polymer applications requiring thermoreversible behavior, including sensing, separations, and functional coatings.  more » « less
Award ID(s):
Author(s) / Creator(s):
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Date Published:
Journal Name:
Polymer Chemistry
Page Range / eLocation ID:
3840 to 3855
Medium: X
Sponsoring Org:
National Science Foundation
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