Multiple Sol‐Gel Transitions of PEG‐PCL‐PEG Triblock Copolymer Aqueous Solution

Abstract

An aqueous solution of a poly(ethylene glycol)-polycaprolactone-poly(ethylene glycol) (PEG-PCL-PEG) with a composition of EG(13) CL(23) EG(13) undergoes multiple transitions, from sol-to-gel (hard gel)-to-sol-to-gel (soft gel)-to-sol, in the concentration range 20.0∼35.0 wt.-%. Through dynamic mechanical analysis, UV-vis spectrophotometry, small angle X-ray scattering, differential scanning calorimetry, microcalorimetry and (13) C NMR spectroscopy, the mechanism of these transitions was investigated. The hard gel and soft gel are distinguished by the crystalline and amorphous state of the PCL. The extent of PEG dehydration and the molecular motion of each block also played a critical role in the multiple transitions. This paper suggests a new mechanism for these multiple transitions driven by temperature changes.

Biomedical Applications of Biodegradable Polyesters

“…Similar to all the other polyesters, there has been a major shift towards the chemical modification of PCL to finely tune the physicochemical properties of the polymer. The chemical copolymerization of caprolactone with functionalized monomers such as lactide [216], ethylene glycol [217,218,219,220], monomethyoxy poly(ethylene glycol) [221], acryloxy [222,223,224], and propylene fumarate [225] is used to form a new class of PCL-based polymers. In these chemical modification approaches, the ring opening polymerization technique is used to copolymerize the building monomer of PCL (caprolactone) with different monomers to ultimately alter the physicochemical properties of the resulting polymers.…”

Temperature-triggered redox-degradable poly(ether urethane) nanoparticles for controlled drug delivery

“…Temperature-responsive amphiphilic polymers undergo a phase transition in aqueous solution due to the cooperative dehydration and intermolecular interactions when the temperature is raised above their LCST. 42,43 To test this behaviour, a solution of PEG1000-co-DiT (1 mg mL À1 ) was heated up to 50 C. A turbid and homogeneous dispersion was observed with increase in temperature and this process was thermally reversible (Fig. 3a).…”

Temperature-induced phase-transitions of methoxyoligo(oxyethylene) styrene-based block copolymers in aqueous solution

“…9 and 10), like Pluronic and PEG-PLGA-PEG. 39 As shown in Fig. 9, the bluish and ow-able sol (20 wt%) became a white gel when heated from 25 C (point a) to 40 C (point b).…”