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.
Highlights
Aqueous solutions of some polymers show reversible phase-transition behavior, such as white turbidity when heated above the lower critical solution temperature (LCST) and dissolving again to clear when cooled below the LCST [1,2,3]
We studied a series of copolymers of Benzyl glycidyl ether (BnGE) and ethyl glycidyl ether (EGE) obtained by statistic/block copolymerization methods, i.e., PBnGE-stat-poly(ethyl glycidyl ether) (PEGE), PBnGE-b-PEGE
In accordance with Scheme 1, PBnGE was first prepared by the t-Bu-P4-catalyzed anionic ring-opening polymerization (ROP) of the monomer BnGE using 4-tert-butylbenzyl alcohol as the initiator, followed by EGE as the M2nd monomer for statistic/block copolymerization
Summary
Aqueous solutions of some polymers show reversible phase-transition behavior, such as white turbidity when heated above the lower critical solution temperature (LCST) and dissolving again to clear when cooled below the LCST [1,2,3]. Sulfobetaine polymers, which are bipolar polymers, are known as polymers showing the upper critical solution temperature (UCST) after phase separation at low temperatures [9,10,11] These polymers have been actively studied from the purely basic interest in clarifying phase-transition phenomena of aqueous solutions of polymers and from the application aspect as intelligent polymers. The phase separation of poly (N-isopropylacrylamide) (PNIPAM) has been analyzed from various aspects using methods such as turbidimetry, calorimetry, nuclear magnetic resonance, fluorescence, light scattering, and neutron scattering [12,13,14] It has been clarified by these studies that the macroscopic phase-separation phenomenon of PNIPAM is accompanied by the shrinkage phenomenon of polymer chains, called coil-globule transition [15,16]. Since the infrared spectrum is sensitive to intermolecular interaction, a series of research was conducted by analyzing the hydration state of polymers using this method [15,18]
Sign-in/Register to view highlights & summary Sign-in/Register to access full text options 
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a callDisclaimer: All third-party content on this website/platform is and will remain the property of their respective owners and is provided on "as is" basis without any warranties, express or implied. Use of third-party content does not indicate any affiliation, sponsorship with or endorsement by them. Any references to third-party content is to identify the corresponding services and shall be considered fair use under The CopyrightLaw.
