Cristalización isotérmica de poli(-caprolactona) en copolímeros en estrella y ramificados
Physicochemical properties of semicrystalline polymers depend, among other characteristics, on their chemical structures and the crystallization conditions used. For example, the size of the crystals, the degree of crystallinity and the microstructure of the crystalline entities formed can be modifi...
Guardado en:
| Autores principales: | , , , , |
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| Formato: | Online |
| Lenguaje: | spa |
| Publicado: |
Facultad de Ciencias Aplicadas a la Industria
2022
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| Acceso en línea: | https://revistas.uncu.edu.ar/ojs3/index.php/revicap/article/view/5998 |
| Sumario: | Physicochemical properties of semicrystalline polymers depend, among other characteristics, on their chemical structures and the crystallization conditions used. For example, the size of the crystals, the degree of crystallinity and the microstructure of the crystalline entities formed can be modified by varying the crystallization conditions. In this sense, the kinetic study of the crystallization process is used to predict final physical properties in semicrystalline polymers, as well as to quantify the energy barriers associated with the process of nucleation and crystal growth. In this work, the isothermal crystallization of poly(HEMA-g-PCL)3 star-grafted copolymers synthesized by the combination of simultaneous ring-opening polymerization (ROP) and reversible chain addition, fragmentation and transfer (RAFT) polymerization was studied, using ε-caprolactone (PCL) and 2-hydroxyethyl methacrylate (HEMA) as monomers. Poly(HEMA-g-PCL)3 copolymers were physicochemically characterized by Fourier transform infrared spectroscopy (FTIR) and Size exclusion chromatography (SEC). By using Differential scanning calorimetry (DSC) and Thermogravimetric analysis (TGA), their thermal transitions and stability were determined. Moreover, the isothermal crystallization kinetics was studied by using DSC technique comparing a linear PCL homopolymer with the synthesized copolymers. By using the Hoffman-Weeks (H-W) theory, kinetic parameters of interest were obtained such as: growth rate and secondary nucleation constant. As more important results, the synthesized poly(HEMA-g-PCL)3 copolymers exhibited molar masses between 27,700 and 61,100 g mol-1, with dispersion values (Ð) less than 1.7. SEC and FTIR analysis confirmed the presence of PCL and PHEMA in the final materials. Regarding the parameters evaluated using the H-W theory, copolymers presented values of global growth rate and secondary nucleation constant lower than those obtained for the linear homopolymer PCL as a consequence of the final branched structure obtained.
Keywords: Controlled synthesis - poly(ε-caprolactone) - poly(2-hydroxyethylmethacrylate) - isothermal crystallization. |
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