Precise Synthesis and Thermoresponsive Property of Poly(ethyl glycidyl ether) and Its Block and Statistic Copolymers with Poly(glycidol)

Abstract

In this paper, we describe a comprehensive study of the thermoresponsive properties of statistic copolymers and multiblock copolymers synthesized by poly(glycidol)s (PG) and poly(ethyl glycidyl ether) (PEGE) with different copolymerization methods. These copolymers were first synthesized by ring-opening polymerization (ROP), which was initiated by tert-butylbenzyl alcohol (tBBA) and 1-tert-butyl-4,4,4-tris(dimethylamino)-2,2-bis[tris(dimethylamino)phosphoranylidenamino]-2Λ5,4Λ5-catenadi(phosphazene) (t-Bu-P4) as the catalyst, and then the inherent protective groups were removed to obtain the copolymers without any specific chain end groups. The thermoresponsive property of the statistic copolymer PGx-stat-PEGEy was compared with the diblock copolymer PGx-b-PEGEy, and the triblock copolymers were compared with the pentablock copolymers. Among them, PG-stat-PEGE, PG-b-PEGE-b-PG-b-PEGE-b-PG, and PEGE-b-PG-b-PEGE-b-PG-b-PEGE, and even the specific ratio of PEGE-b-PG-b-PEGE, exhibited LCST-type phase transitions in water, which were characterized by cloud point (Tcp). Although the ratio of x to y affected the value of the Tcp of PGx-stat-PEGEy, we found that the disorder of the copolymer has a decisive effect on the phase-transition behavior. The phase-transition behaviors of PG-b-PEGE, part of PEGE-b-PG-b-PEGE, and PG-b-PEGE-b-PG copolymers in water present a two-stage phase transition, that is, firstly LCST-type and then the upper critical solution temperature (UCST)-like phase transition. In addition, we have extended the research on the thermoresponsive properties of EGE homopolymers without specific α-chain ends.

Polyethers Based on Short-Chain Alkyl Glycidyl Ethers: Thermoresponsive and Highly Biocompatible Materials

“…Via statistical copolymerization, an incorporation of 30% EGE units was necessary to observe a T cp . Surprisingly, diblock copolymers of PEGE and P­( lin G) exhibited no T cp for all compositions from 10 to 50 mol % of linear glycerol units for molecular weights between 11 and 13.5 kg mol –1 . However, PEGE- b -P­( lin G)- b -PEGE triblock copolymers with an overall PEGE content of 70% showed a T cp at 50.6 °C.…”

“…Recently, Kakuchi and co-workers investigated the impact of microstructure with regard to thermal phase-transition behavior as they compared P­( lin G- co -EGE) to P­( lin G)- b -PEGE copolymers (Figure ). Copolymers with varied comonomer compositions were investigated, while comparability of the results was ensured as copolymers of equal M n between 8.8 and 9.7 kg mol –1 were compared. Generally, T cp values between 30.5 and 70.4 °C were obtained for statistical copolymers with EGE content >20%.…”

“…Transmittance vs temperature illustrating the thermal properties in aqueous solution (10 mg mL –1 , 500 nm) of P­( lin G- co -EGE) (in the original article designated as PG- stat -PEGE) (a) and P­( lin G)- b -PEGE (b). Reprinted from ref , licensed under CC-BY 4.0 10.…”

“…Despite the many advantages offered by utilization of phosphazene bases, their high cytotoxicity and the required rigorous removal after polymerization are prohibitive, if polymers for bioapplication are desired . Very recently, Kakuchi and co-workers investigated the thermoresponsive properties of statistical as well as block copolymers consisting of PEGE and P­( lin G) . P­( lin G) was obtained via polymerization of benzyl glycidyl ether and post-polymerization reduction via H 2 and Pd/C.…”

“…Surprisingly, diblock copolymers of PEGE and P(linG) exhibited no T cp for all compositions from 10 to 50 mol % of linear glycerol units for molecular weights between 11 and 13.5 kg mol −1 . 80 In contrast to the reduction of T cp in highly polar polyethers, the incorporation of GME was used to increase the hydrophilicity of otherwise nonsoluble PPO in aqueous solution. The increase resulted in a T cp of 35 °C in random P(PO-co-GME) copolymers, which is promising for the medical applications in the physiological temperature range.…”