Core-First Synthesis and Thermoresponsive Property of Three-, Four-, and Six-Arm Star-Shaped Poly(N,N-diethylacrylamide)s and Their Block Copolymers with Poly(N,N-dimethylacrylamide)

Abstract

A series of three-, four-, and six-arm star-shaped poly­(N,N-diethylacrylamide)­s (s-PDEAM3, s-PDEAM4, and s-PDEAM6, respectively) and PDEAM-block-poly­(N,N-dimethylacrylamide)­s (s-(PDEAM-b-PDMAM)3,4,6 and s-(PDMAM-b-PDEAM)3,4,6) were synthesized by the core-first group transfer polymerization using core initiators possessing three, four, and six silyl ketene acetals, respectively. The thermoresponsive property of s-PDEAM was compared with that of a linear PDEAM (l-PDEAM), and that of s-(PDEAM-b-PDMAM) and s-(PDMAM-b-PDEAM) was compared with that of linear di- and triblock copolymers, l-PDEAM-b-PDMAM, l-PDEAM-b-PDMAM-b-PDEAM, and l-PDMAM-b-PDEAM-b-PDMAM. Both aqueous solutions of s-PDEAM and s-(PDEAM-b-PDMAM) exhibited lower critical solution temperatures (LCSTs), which were characterized using the cloud point (T c). For the s-PDEAM with different weight average molecular weights (M w,MALSs), T c very slightly changed within 1.0 °C. The thermoresponsive behavior of s-(PDEAM-b-PDMAM) is basically similar to those of l-(PDEAM-b-PDMAM) and l-(PDEAM-b-PDMAM-b-PDEAM). The aqueous solution of s-(PDMAM-b-PDEAM) first shows an LCST-type and then an upper critical solution temperature (UCST)-like (actually not UCST) phase transition, that is, the two-stage phase transition. These thermoresponsive behaviors are confirmed using hydrodynamic radii (R hs) by dynamic light scattering measurements.

Features of Solution Behavior of Polymer Stars with Arms of Poly-2-alkyl-2-oxazolines Copolymers Grafted to the Upper Rim of Calix[8]arene

“…where the contraction factor is g = 0.19 at f a = 8. For the studied CA8-PAlOx, the value of g can be calculated using the empirical equation [59] g = (1.104 − 0.104g 7 )g 0.906 (11) The g values for CA8-PAlOx with copolymer arms lie between the theoretical values of the contraction factor for star-shaped macromolecules with short and long arms (Table 2). This behavior is in agreement with the findings of the study of six-arm polypeptoids [49], which can be considered as long-arm molecules if the arms contain more than six Kuhn segments.…”

“…The use of copolymers as arms is a convenient way to control the properties of stimulus-sensitive star polymers. In the case of block copolymer arms, the sequence of block attachment affects both the phase separation temperatures and the dimensions of supramolecular structures present in solutions [ 11 , 12 , 13 , 14 ]. For example, the variation in solution behavior was observed for triblock copolymer stars with arms consisting of hydrophobic, hydrophilic, and thermosensitive blocks.…”

“…When the thermosensitive block was located near a core, intramolecular aggregation took place and aggregates with a smaller diameter were formed in comparison with the supramolecular structures formed in solutions of macromolecules with a thermosensitive block in the outer layer [12]. From general considerations, it is clear that the stimulus-sensitivity of copolymer stars depends on the ratio of the components [11,[15][16][17][18][19].…”

Precision synthesis for well-defined linear and/or architecturally controlled thermoresponsive poly(N-substituted acrylamide)s

“…Fig. 9 also plots the results of PDEA 164 (concentration = 10 g L −1 , heating rate = 1.0 °C min −1 ) and PiPMA 68 (concentration = 1 wt%, heating rate = 1.0 °C min −1 ) prepared by organocatalytic GTPs. The inversive relationship between M and T cp was well clarified in PiPMA: as the M increased from 3700 to 64 700 g mol −1 , the T cp decreased from 27.5 to 12.0 °C.…”

Thermoresponsive Poly(N,N-diethylacrylamide-co-glycidyl methacrylate) Copolymers and Its Catalytically Active α-Chymotrypsin Bioconjugate with Enhanced Enzyme Stability

“…[ 66 , 67 , 68 , 69 , 70 , 71 , 72 , 73 , 74 , 75 , 76 , 77 , 78 , 79 , 80 , 81 , 82 , 83 , 84 , 85 , 86 , 87 , 88 , 89 , 90 , 91 , 92 ] and references therein). It should also be mentioned that aqueous PDEAAm solutions possess similar critical solution temperatures (CST) [ 72 , 93 , 94 , 95 , 96 ] in the range of ~25–40 °C than that of PNIPAAm [ 46 , 55 ]. On the other hand, although some block copolymers with PDEAAm and poly(glycidyl methacrylate) (PGMA) segments have been prepared and studied [ 91 , 92 ], random copolymers of DEAAm with GMA, which provides reactive pendant epoxy functionalities for the thermoresponsive PDEAAm, and its utilization for polymer-based protein engineering have not been reported so far according to the best of our knowledge.…”