Melt crystallization and morphology of poly(ε‐caprolactone)‐poly(ethylene glycol) diblock copolymers with different compositions and molecular weights

Abstract

Ring opening polymerization of e-caprolactone was realized in the presence of monomethoxy poly(ethylene glycol) with M n ¼ 1000 and 2000, using Zn(La) 2 as catalyst. The resulting PCL-PEG diblock copolymers with CL/EO repeat unit molar ratios from 0.2 to 3.0 were characterized by using DSC, WAXD, SEC, and 1 H NMR. The crystal phase of PCL blocks exist in all polymers, and the crystallization ability of PCL blocks increases with CL/EO ratio. PEG blocks are able to crystallize for copolymers with CL/EO below 1.0 only. Melt crystallization results were analyzed with Avrami equation. The Averami exponent n is around 3.0 in most cases, in agreement with heterogeneous nucleation with three dimensional growth. The morphology of the crystals was observed by using POM. Rod-like crystals were found to grow in 1, 3 or 2, 4 quadrants for samples with low molecular weights. In the case of a copolymer with M n,PEG ¼ 2000 and M n,PCL ¼ 800, PEG blocks could crystallize and grow on PCL crystals after PCL finished to form rod-like crystals, leading to formation of poorly or well structured spherulites. The spherulite growth rate (G) was determined at different crystallization temperatures (T c ) ranging from 9 to 49 C. All the copolymers present a steady G decrease with increasing crystallization temperature due to lower undercooling. On the other hand, increase of CL/EO ratio leads to increase of G in the same T c range.

Self‐assembled micelles prepared from poly(ɛ‐caprolactone)–poly(ethylene glycol) and poly(ɛ‐caprolactone/glycolide)–poly(ethylene glycol) block copolymers for sustained drug delivery

“…In the spectra of the copolymers, the diffraction peak of PEG at 19.4° and that of PCL at 21.4° are observed, whereas the peak of PEG at 23.3° overlaps with that of PCL at 23.7°. These findings demonstrate that both the PCL and PEG components are able to crystallize in the copolymers, as reported in the literature . The introduction of the PGA component, which could not crystallize due to its low content, did not affect the crystalline structure of the PCL‐PEG copolymers.…”

Design and Evaluation of Multifunctional Nanocarriers for Selective Delivery of Coenzyme Q10 to Mitochondria

“…49,50 The thermogram of PEG2-PCL3.8-TPPBr alone shows two distinct endothermic peaks at 45.85 and 52.79°C, attributed, respectively, to the melting of PEG and PCL. 51 These two melting events suggest the existence of two distinct crystalline domains in the miktoarm polymer. 30 CoQ10/PEG2-PCL3.8-TPPBr physical mixture shows the same characteristic melting peaks for both CoQ10 and PEG2-PCL3.8-TPPBr copolymer ( Figure 4B).…”

Solubility considerations in relative block crystallization and morphology of PEO‐ b ‐PCL films

“…The cooling thermograms for 5k5k, 5k10k, 5k16.3k, and 5k24.5k PEO-b-PCL are shown in Figure 1. The first peak is assigned to PCL crystallization because of its larger weight fraction, [17][18]21,[23][24][25][26][27][28][29][30][31][32][33][34][35] and therefore the second peak (indicated by arrows) was assigned to PEO crystallization. Onset Txs were determined for both PCL and PEO using Pyris software.…”

“…PEO-b-PCL block copolymer crystallization has been studied extensively (see, for example, Refs. [21][22][23][24][25][26][27][28][29][30][31][32][33][34] because PEO and PCL homopolymer Tms are similar.…”