Abstract
In this study, polylactide/urea complexes were successfully prepared by the electrospinning method, then the host urea component was removed to obtain a coalesced poly(l-lactide) (PLLA)/poly(d-lactide) (PDLA) blend. The crystallization behavior of the coalesced PLLA/PDLA blend (c-PLLA/PDLA) was studied by a differential scanning calorimeter (DSC) and Fourier transform infrared (FTIR) spectroscopy. The c-PLLA/PDLA was found to show better crystallization ability than normal PLLA/PDLA blend (r-PLLA/PDLA). More interestingly, the c-PLLA/PDLA effectively and solely crystallized into stereocomplex crystals during the non-isothermal melt-crystallization process, and the reason was attributed to the equally-distributing state of PLLA and PDLA chains in the PLLA/PDLA/urea complex, which led to good interconnection between PLLA and PDLA chains when the urea frameworks were instantly removed.
Highlights
Polylactide (PLA) has become one of the most important and commercial biodegradable polymers because it possesses comparable mechanical and thermal properties with polyolefin materials [1].due to the rigid chain structure and relative high glass transition temperature, it shows many drawbacks, such as a low crystallization rate and poor heat resistance; subsequently, the practical applications of PLA are remarkably restricted [2,3,4]
differential scanning calorimeter (DSC) measurement was performed to determine the formation of inclusion complex between PLLA
The new melting point, which was consistent with previous reports on other polymer/urea complexes, indicated the successful preparation of the PLLA/urea inclusion complex [42]
Summary
Polylactide (PLA) has become one of the most important and commercial biodegradable polymers because it possesses comparable mechanical and thermal properties with polyolefin materials [1].due to the rigid chain structure and relative high glass transition temperature, it shows many drawbacks, such as a low crystallization rate and poor heat resistance; subsequently, the practical applications of PLA are remarkably restricted [2,3,4]. The stereocomplex crystals show stronger inter-chain interaction, have a much higher melting point (~225 ◦ C), and display a faster crystallization rate than homocrystallite of either PLLA or PDLA [16,17,18], resulting in higher mechanical strength and modulus, better heat resistance, etc. The formations of the stereocomplex and homocrystallite are competing during the crystallization process in the PLLA/PDLA blend [22,23]. The formation of the stereocomplex can be sharply inhibited as the PLA molecular weight increases [24,25,26]. The intrinsic occupied space leads to the steric repulsion effect among different chains, which goes against the contact between PLLA and PDLA segments, and benefits the formation of homocrystallite.
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