Abstract
In this work, the morphological and conformational evolution of bio-based polyethylene glycol (PEG)-acrylic rosin polymer in water was studied by scanning electron microscopy (SEM), polarized optical microscopy (POM), differential scanning calorimetry (DSC), X-ray diffraction (XRD), Rayleigh light scattering (RLS) and dynamic light scattering (DLS) techniques during a heating and cooling cycle. When the concentration was higher than the critical micelle concentration (CMC), a reversible transformation process, i.e. from micelle to irregular lamella aggregations, was detected. As the concentration was equal to or below the CMC, individual unimers aggregated into needle-shaped crystals composed of acrylic rosin crystalline core in the heating run. The crystallization of acrylic rosin blocks acted as seeds and thus, in the subsequent cooling process, the PEG corona crystallized into the cube-shaped crystals. The cytotoxicity assay showed the biocompatibility of bio-based polyethylene glycol-acrylic rosin polymer. This has great potential in the application of drug delivery and release triggered by temperature.
Highlights
A great deal of research has focused on the phase evolution of coil-coil [1,2,3] and crystalline-coil [4,5,6]block polymers
The morphological changes of bio-based polyethylene glycol (PEG)-acrylic rosin polymer in water over a wide temperature range was investigated with scanning electron microscopy (SEM)
When concentration was equal to or below critical micelle concentration (CMC), the morphologies from individual unimers to needle and to cube-like crystals were investigated within one heating-cooling cycle
Summary
Little attention has focused on double-crystalline block polymers. The phase evolution and crystallization behavior of the double-crystalline copolymer might be more complex than the crystalline-amorphous block polymer. Li et al [13] studied the crystallization and self-assembly behavior of PE-b-PEO and indicated that spherical micelles consisting of crystalline multi cores could be formed, though the crystallization process of poly(ethylene oxide) (PEO) and PE was seriously restricted through the PE-b-PEO assembled structure in aqueous solution. Van Horn et al studied the crystallization process for PEO-PCL double crystalline block polymers in solution and demonstrated that the smaller weight fraction crystallized first into the lamellar single crystal, and subsequently, the tethered chains crystallized into lamellar crystals by being preferentially oriented upon the surface due to the crystallization
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