Synthesis and characterizations of poly(ethylene-co-vinylalcohol)-grafted-poly(3-hydroxybutyrate-co-hydroxyvalerate) copolymers

Paula ML, M. de Moraes R, Alves GM, M. Lacerda T, dos Santos JC, M. dos Santos A, Medeiros SDF. Chemical Modification of Pullulan Exopolysaccharide by Grafting Poly(3-hydroxybutyrate-co-3-hydroxyvalerate) (PHBHV) via Click Chemistry

Biodegradable and biocompatible copolymers have been often studied for the development of biomaterials for drug delivery systems. In this context, this work reports the synthesis and characterization of a novel pullulan-g-poly(3-hydroxybutyrate-co-3-hydroxyvalerate) (Pull-g-PHBHV) graft copolymer using click chemistry. Well-defined and functional pullulan backbones containing azide groups (PullN₃) previously prepared by our group were successfully used for this purpose and propargyl-terminated poly(3-hydroxybutyrate-co-3-hydroxyvalerate) was prepared via transesterification using propargyl alcohol as a chain transfer agent. By an alkyne-azide cycloaddition reaction catalyzed by copper (Cu (I)) (CuAAC), the graft copolymer Pull-g-PHBHV was obtained. The chemical structures of the polymers were accessed by ¹H NMR and ¹³C NMR FTIR. Disappearance of the bands referring to the main bonds evidenced success in the grafting reaction. Besides that, DRX, DSC and TGA were used in order to access the changes in crystallinity and thermal behavior of the material. The remaining crystallinity of the Pull-g-PHBHV structure evidences the presence of PHBHV. Pull-g-PHBHV presented lower degradation maximum temperature values than the starting materials, indicating its minor thermal stability. Finally, the synthesized material is an innovative biopolymer, which has never been reported in the previous literature. It is a bio-derived and biodegradable polymer, chemically modified, resulting in interesting properties which can be useful for their further applications as biomedical systems for controlled delivery, for example.

Bioinspired EVAL membrane modified with cilia-like structures showing simultaneously enhanced permeability and antifouling properties

A simple and effective strategy to simultaneously enhance the permeability and antifouling properties of ethylene vinyl alcohol (EVAL) membrane was developed based on the bioinspired natural cleaner, cilia. Taking clue from the self-cleaning effect of cilia, supramolecular polyrotaxanes (PRs) with sliding and rotating cyclic molecules along linear chains were synthesized using azide-alkyne click chemistry. Cilia-like PRs were incorporated into EVAL matrix in the fabrication of modified EVAL membranes. Cilia-like structures protruding from the membrane surface have been observed by SEM, TEM and AFM. By imitating natural ciliary movements, these structures provided a proactive self-cleaning system to remove the foulants. The introduction of cilia-like PRs enhanced the surface roughness and hydrophilicity, and significantly enhanced permeability by 55.3% compared to raw EVAL membrane. Moreover, the membrane modified with cilia-like PRs showed an excellent antifouling property with a lower water flux decline (12.6%) and higher water flux recovery (94%) in dynamic fouling tests. Furthermore, this modified membrane develops the scope of bioinspired membranes, inspiring more attractive potential applications in self-cleaning materials, dynamic membranes and supramolecular machines.