Polymer Terminal Group Effects on Properties of Thermoresponsive Polymeric Micelles with Controlled Outer-Shell Chain Lengths

Abstract

Well-defined amphiphilic diblock copolymers comprising thermoresponsive polymer segments of poly(N-isopropylacrylamide-co-N,N-dimethylacrylamide) (PID) and hydrophobic polymer segments, poly(benzyl methacrylate) (PBzMA), were synthesized by controlled living radical polymerization. Terminal derivatization of PID segments to either hydroxyl or phenyl groups was achieved through reactions of coupling agents with thiol groups exposed by cleavage of terminal dithiobenzoate groups. Diblock copolymers formed core-shell type polymeric micelles with thermoresponsive outer shells. Hydrodynamic micellar diameters ranged from 12 to 31 nm, controlled by varying PID chain lengths. Differences in PID terminal groups did not affect the critical micelle concentration or micellar diameters. However, these groups demonstrated a significant influence on the micellar thermoresponses. Hydroxylated PID/PBzMA micelles exhibited a phase transition of approximately 40 degrees C, independent of PID molecular weights. Even though molecular weights and compositions of PID chains were equivalent except for terminal groups, micelles having the outermost surface phenyl groups exhibited drastically lower phase transition temperature shifts, especially for micelles with low molecular weight PID chains.

Temperature-Responsive Polymer Modified Surface for Cell Sheet Engineering

“…With this new approach, a cell adhesion/de-adhesion surface can be prepared easily by varying polymerization time. Moreover, a "living" reactive group has been reserved in the terminal of polymer chain, which can produce various block copolymers via multistep RAFT polymerization [62,63]. Utilizing this unique property, a micropatterned temperature-responsive polymer brush surface has been fabricated to obtain a cell sheet with a well-controlled orientational structure [64].…”

Thermoresponsive hyperbranched polyethylenimines with isobutyramide functional groups

“…2 To date, the fundamental composition in nearly all the thermoresponsive materials was the linear polymers with LCST property. [3][4][5] In other words, even though the thermoresponsive materials had some specific topology, such as hydrogel, 6 star or grafted polymer, [7][8][9] and polymeric micelles, 10,11 their LCST properties were only contributed by their fundamental composition of the thermoresponsive linear polymer, and were independent on their specific topology. Only very recently, perfectly branched and welldefined dendrimers exhibiting the LCST in aqueous media were addressed, and the LCSTs were significantly dependent on the spheroid-like geometry of dendrimers.…”

Successful in vivo hyperthermal therapy toward breast cancer by Chinese medicine shikonin-loaded thermosensitive micelle

“…A reversible addition-fragmentation chain transfer (RAFT) agent, 2-(N-[2-hydroxyethyl]carbamoyl) prop-2-yl dithiobenzoate (HECPD), was prepared according to previous publications. 28,[31][32][33] The water used was purified by a Milli-Q water purification system (EMD Millipore, Billerica, MA, USA). The dialysis membrane was provided by Spectrum Medical Industries (Los Angeles, CA, USA).…”