Collapse of Cylindrical Brushes with 2‐Isopropyloxazoline Side Chains Close to the Phase Boundary

Abstract

A high-molar-mass cylindrical brush polymer with a main chain degree of polymerization of Pw = 1047 is synthesized by free-radical polymerization of a poly-2-isopropyloxazoline macromonomer with Pn = 28. The polymerization is conducted above the lower phase transition temperature of the macromonomer, i.e., in the phase-separated regime, which provides a sufficiently concentrated macromonomer phase mandatory to obtain high-molar-mass cylindrical brushes. Upon heating to the phase transition temperature, the hydrodynamic radius is observed to shrink from 34 to 27 nm. Further increase in temperature resulted in aggregated chains which were observed to coexist with single chains until eventually only aggregates of μm size were detectable.

Poly(2-oxazoline) molecular brushes by grafting through of poly(2-oxazoline)methacrylates with aqueous ATRP

“…48,50,51,[53][54][55][56] The transmittance of aqueous solutions (1 wt%) of the brushes was observed in dependency of the temperature and the cloud point (T CP ) was determined at 10 % decrease in optical transmittance ( Figure 7). 48,50,51,[53][54][55][56] The transmittance of aqueous solutions (1 wt%) of the brushes was observed in dependency of the temperature and the cloud point (T CP ) was determined at 10 % decrease in optical transmittance ( Figure 7).…”

“…8,[18][19][20] Furthermore, multiple functionalization and structural versatility is possible using respective initiators, monomers and terminating agents. 50 Alternatively, in different grafting from approaches, 2-isopropenyl-2oxazoline was polymerized using FRP, anionic polymerization or rare earth metal catalyzed GTP to create a backbone from which different 2-oxazolines were polymerized via living cationic ring-opening polymerization (LCROP) to yield molecular brushes. The majority of the applied methods focuses on the polymerization of macromonomers by group transfer polymerization (GTP), free radical polymerization (FRP) or reversible addition/fragmentation chain transfer polymerization (RAFT).…”

“…GTP and RAFT can result in molecular brushes with narrow molar mass distributions, but are still limited to relatively short backbones and side chains. 48,50,51,[53][54][55][56] Thus, POx molecular brushes are interesting materials to be used as sensors or, with a cloud points adjustable close to the human body temperature, for biomedical applications such as theragnostics. 48 Nevertheless, RAFT has successfully been used for the synthesis of copolymer molecular brushes made from short (P n = 5) 2-ethyl-and 2-nonyl-2-oxazoline macromonomers.…”

Synthesis and Investigation of Double Stimuli-Responsive Behavior ofN-Isopropylacrylamide and Maleic Acid Copolymer in Solutions

“…ACCEPTED MANUSCRIPT 19 The maximum values of t eq obtained for poly(NIPAAm-co-MA) solutions were considerably larger than the duration of kinetic processes which have been observed for such stimuliresponsive polymers as poly(2-isopropyl-2-oxazoline), poly(alkyl-2-oxazoline) block copolymers, PDMAEMA block copolymers, some thermosensitive cationic diblock copolymers, polystyrene/poly(N-isopropylacrylamide) core-shell nanoparticles, and cylindrical brushes with 2-Isopropyloxazoline side chains [39][40][41][42][43][44]). In order to explain the high time durations for reaching plateau values of the solution characteristics after a temperature jump, we make the following assumptions.…”

“…In order to explain the high time durations for reaching plateau values of the solution characteristics after a temperature jump, we make the following assumptions. Firstly, in the overwhelming majority of works low-concentration solutions (c £ 0.001 g cm -3 ) were investigated using light scattering [28,[39][40][41][42][43][44][45][46], whereas the concentration of the investigated poly(NIPAAm-co-MA) solutions was 0.0150 g cm -3 . However, the time required for equilibrium achievement depends strongly on concentration, decreasing rapidly with decreasing c [31]; thus t eq might decrease for low-concentration poly(NIPAAm-co-MA) solutions.…”