Synthesis of PCL–PEG–PCL Triblock Copolymer via Organocatalytic Ring-Opening Polymerization and Its Application as an Injectable Hydrogel—An Interdisciplinary Learning Trial

Abstract

Biocompatible and biodegradable block copolymers composed of poly­(ethylene glycol) (PEG) and aliphatic polyester are a class of promising biomaterials. Herein, a teaching experiment was designed to furnish undergraduates with a reliable method to synthesize an amphiphilic poly­(ε-caprolactone)-PEG-poly­(ε-caprolactone) (PCL–PEG–PCL) triblock copolymer via ring-opening polymerization of ε-caprolactone using PEG as the macroinitiator and diphenyl phosphate as the green organocatalyst; the concentrated solution of synthetic polymer in water was then demonstrated as an injectable thermogel with a sol–gel transition upon heating. Ten students serving as volunteers successfully synthesized PCL–PEG–PCL copolymer, and then analyzed their specimens using various techniques including proton-nuclear magnetic resonance spectroscopy, gel permeation chromatography, differential scanning calorimetry, and X-ray diffraction and learned the principles of instruments. Finally, students prepared an aqueous polymer solution, and observed its interesting spontaneous physical gelation upon heating via the tube-inverting approach and dynamic rheological analysis. The experimental features captured the students’ attention and made them more enthusiastic participants. This newly designed teaching experiment afforded senior undergraduates an excellent opportunity to consolidate basic concepts and principles in books with practical experimental sessions in the field of polymer chemistry, analytical chemistry, and materials science.

Decisive Influence of Hydrophobic Side Chains of Polyesters on Thermoinduced Gelation of Triblock Copolymer Aqueous Solutions

“…In the cooling curves, the broad exothermic peaks at around −15 to 10 °C appeared, which reflected the crystallization transitions of the copolymers. For thermosensitive PCL–PEG–PCL triblock copolymers with similar MWs, the melting transitions and crystallization transitions of PCL blocks usually locate at 40–60 °C and 10–35 °C, respectively. ,, The random copolymerization of a small amount of 5-alkyl δ-lactones bearing various side groups noticeably hinders the crystallization of PCL domain, resulting in significant decreases both in the T m and crystallization temperature ( T c ) of the polyester blocks.…”

An Intelligent Transdermal Formulation of ALA‐Loaded Copolymer Thermogel with Spontaneous Asymmetry by Using Temperature‐Induced Sol–Gel Transition and Gel–Sol (Suspension) Transition on Different Sides

“…Sol-Gel and Gel-Sol (Suspension) Transitions with Temperature: Test-tube inversion method was used to investigate the transition temperatures of copolymer aqueous solutions. [95,96] First, copolymer solutions were made with different ratios of copolymer-1/copolymer-2 (1:0, 2:1, 1:1, 1:2, 0:1). Second, 0.5 mL of each polymer aqueous solution was put into a small vial.…”

Coordination Insertion Mechanism of Ring‐Opening Polymerization of Lactide Catalyzed by Stannous Octoate†

“…[ 84 ] Most of biodegradable polyesters such as PLA and their copolymers are obtained via ring opening of cyclic esters assisted by Sn(Oct) 2 and ROH. [ 85‐88 ] The underlying mechanism of the coordination‐insertion ROP of LA in presence of Sn(Oct) 2 and ROH is thus much required to be explored. The present research deepens the microscopic understanding of the polymerization process of lactide.…”