Abstract
The non-isothermal crystallization behaviors of poly (ethylene glycol) (PEG) and poly (ethylene glycol)-b-poly(ε-caprolactone) (PEG-PCL) were investigated through a commercially available chip-calorimeter Flash DSC2+. The non-isothermal crystallization data under different cooling rates were analyzed by the Ozawa model, modified Avrami model, and Mo model. The results of the non-isothermal crystallization showed that the PCL block crystallized first, followed by the crystallization of the PEG block when the cooling rate was 50–200 K/s. However, only the PEG block can crystallize when the cooling rate is 300–600 K/s. The crystallization of PEG-PCL is completely inhibited when the cooling rate is 1000 K/s. The modified Avrami and Ozawa models were found to describe the non-isothermal crystallization processes well. The growth methods of PEG and PEG-PCL are both three-dimensional spherulitic growth. The Mo model shows that the crystallization rate of PEG is greater than that of PEG-PCL.
Highlights
Differential scanning calorimetry (DSC) is commonly used to study the crystallization behavior of polymers [1,2,3,4,5]
We found that the crystallization behavior of poly (ethylene glycol)-b-poly(ε-caprolactone) (PEG-PCL) and PEG observed by FDSC is not completely consistent with the results observed through conventional DSC
For PEG-PCL, we found that when the cooling rate is 50 K/s–200 K/s, the PCL block crystallizes first and the PEG segment crystallizes, which is consistent with the conventional DSC observation results
Summary
Differential scanning calorimetry (DSC) is commonly used to study the crystallization behavior of polymers [1,2,3,4,5]. Its ultra-fast heating rate can greatly inhibit the structural rearrangement during the heating process This phenomenon shows its unique advantages in the crystallization research of many polymer materials. Different methods have been developed to evaluate non-isothermal crystallization based on DSC experimental data, such as Ozawa model, Avrami model, Mo model, etc., [12,13,14] Some of these methods can be better explained in the DSC experimental data obtained at a lower cooling rate [15,16,17,18]. We selected the homopolymer PEG and block copolymer PEG-PCL to study their non-isothermal crystallization behavior under a high cooling rate measured by FDSC. The Ozawa model, Avrami model, and Mo model are used to evaluate the non-isothermal crystallization behavior of PEG and PEG-PCL at high cooling rates, and compare the results with the non-isothermal crystallization results by DSC
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