Solution Behavior of Temperature‐Responsive Molecular Brushes Prepared by ATRP

Abstract

Molecular brushes, with side chains consisting of two copolymers: 2‐(dimethylamino)ethyl methacrylate with methyl methacrylate, and N,N‐dimethylacrylamide with butyl acrylate were prepared by grafting‐from via atom transfer radical polymerization (ATRP). Poly(2‐(2‐bromoisobutyryloxy)ethyl methacrylate) and poly(2‐(2‐bromopropionyloxy)ethyl methacrylate) were used as macroinitiators. Dynamic light scattering (DLS) studies were performed for aqueous solutions of molecular brushes below and above the lower critical solution temperature (LCST), and an unusual concentration‐dependent LCST was observed. Due to the compact structure of molecular brushes, intramolecular collapse can occur when the average distance between molecules is much larger than the hydrodynamic dimensions of the individual macromolecules. However, if the concentration of the solution of molecular brushes is increased to the level in which the separation distance is comparable with the brush hydrodynamic dimensions, intermolecular aggregation occurs, as typically observed for solutions of linear polymers.magnified image

Thermoresponsive Polyphosphazene‐Based Molecular Brushes by Living Cationic Polymerization

“…The polyphosphazenes backbone is known to be highly flexible and similar polymers with N‐isopropylacrylamide oligomers grafted to a polyphosphazene backbone have been shown to form micelles and temperature‐triggered nanospheres . Internal inter‐chain aggregation within one molecular brush polymer could also be expected . It is possible that a shrinkage of the individual polymer chains occurs prior to and/ or during aggregation, due to a coil‐to‐globule transition within only one molecular brush type polymer .…”

Methods of controlled radical polymerization for the synthesis of polymer brushes

“…Polymer brushes with thermosensitive polymer side chains, such as poly(N isopropylacrylamide) [150] and poly(N,N dimethylaminoethyl methacrylate) (PDMAEMA) [151][152][153][154][155], which are usually obtained via the ATRP method, are the focus of considerable attention from researchers. The latter polymer addi tionally exhibits clearly pronounced polycationic properties.…”

Synthetic Strategies towards Well‐Defined Complex Polymeric Architectures through Covalent Chemistry

“…In addition, the physical properties of molecular brush polymers are often affected by the sidechain grafting density, length, stiffness and composition [5]. Molecular brush polymers have demonstrated potential applications in micro-mechanical applications serving as miniature cushions [119], molecular pistons [120,121] and artificial muscles [117]. Molecular brush polymers have demonstrated potential applications in micro-mechanical applications serving as miniature cushions [119], molecular pistons [120,121] and artificial muscles [117].…”

“…9). Controlled/living polymerization techniques such as living anionic polymerization [134,135] and ATRP [136] are often employed for brush polymer syntheses via the grafting-from approach since intramolecular and intermolecular termination events that lead to macrocyclic side chains and/or macroscopic gelation are minimized. Controlled/living polymerization techniques such as living anionic polymerization [134,135] and ATRP [136] are often employed for brush polymer syntheses via the grafting-from approach since intramolecular and intermolecular termination events that lead to macrocyclic side chains and/or macroscopic gelation are minimized.…”

“…Controlled/living polymerization techniques such as living anionic polymerization [134,135] and ATRP [136] are often employed for brush polymer syntheses via the grafting-from approach since intramolecular and intermolecular termination events that lead to macrocyclic side chains and/or macroscopic gelation are minimized. Through controlled/living polymerization techniques, brush polymers with various functional side-chains have been synthesized using acrylic [139,140], methacrylic [121,136,141], acrylamide [142] and styrenic [143,144] monomers. However, compared to the grafting-through approach (Sect.…”