Synthesis and characterization of polyvinyl alcohol based semi interpenetrating polymeric networks

Moisture Adsorption-Desorption Behaviour in Nanocomposite Copolymer Films

Dehumidifying air via refrigerant cooling method consumes a tremendous amount of energy. Independent humidity control systems using desiccants have been introduced to improve energy efficiency. This research aimed to find an alternative to the commonly used solid desiccant, silica gel, which has weak physical adsorption properties. It also aimed to overcome the limitation of liquid desiccants that may affect indoor air quality and cause corrosion. This study reports on the synthesis of poly(vinyl alcohol-co-acrylic acid), P(VA-AA), through solution polymerisation by hydrolysing poly(vinyl acetate-co-acrylic acid), P(VAc-AA). This viable copolymer was then incorporated with graphene oxide (GO) at different concentrations (0 wt.%, 0.5 wt.%, 2 wt.% and 5 wt.%) to enhance the adsorption-desorption process. The samples were tested for their ability to adsorb moisture at different levels of relative humidity (RH) and their capability to maintain optimum sorption capacity over 10 repeated cycles. The nanocomposite film with 2% GO, P(VA-AA)/GO2, exhibited the highest moisture sorption capacity of 0.2449 g/g for 60-90% RH at 298.15 K, compared to its pristine copolymer, which could only adsorb 0.0150 g/g moisture. The nanocomposite desiccant demonstrated stable cycling stability and superior desorption in the temperature range of 318.15-338.15 K, with up to 88% moisture desorption.

Synthesis of photodegradable cassava starch-based double network hydrogel with high mechanical stability for effective removal of methylene blue

Synthetic hydrogel has been widely used in several applications, but poor mechanical stability and biodegradability limit their applications and raise environmental concerns. Here, a biodegradable hydrogel was developed via simple free-radical polymerization of poly(acrylic acid) (PAA) in the presence of cassava starch (CS) and poly(vinyl alcohol). The hydrogel showed exceptional mechanical and physical properties. The structural morphology changed at higher CS content from a dense fiber-like porous network to larger pores with thicker cell walls. Due to the formation of a double network structure via physical entanglement, the compressive modulus significantly increased from 27 kPa (CS 0 wt%) to 127 kPa (CS 50 wt%). Reducing synthetic content (PAA) to 25 wt% and increasing CS content to 50 wt% did not reduce the removal efficiency of the hydrogel toward methylene blue (MB). The maximum adsorption capacity of the CS50 hydrogel was 417.0 mg/g. Data fitting to theoretical models indicated monolayer adsorption of MB on a homogeneous surface via chemisorption. Removal efficiency was higher than 70% at the 5^th cycle of adsorption-desorption. The biodegradability and photodegradability of the hydrogel were improved by grafting with CS. The developed hydrogel represents an alternative biodegradable adsorbent for a sustainable system of wastewater treatment.

Controlled delivery of ibuprofen from poly(vinyl alcohol)-poly(ethylene glycol) interpenetrating polymeric network hydrogels

Hydrogels composed of poly(vinyl alcohol) (PVA) and poly(ethylene glycol) (PEG) were synthesized using glutaraldehyde as crosslinker and investigated for controlled delivery of the common anti-inflammatory drug, ibuprofen (IBF). To regulate the drug delivery, solid inclusion complexes (ICs) of IBF in β–cyclodextrin (β–CD) were prepared and added to the hydrogels. The ICs were prepared by the microwave irradiation method, which is more environmentally benign. The formation of IC was confirmed by various analytical techniques and the synthesized hydrogels were also characterized. Controlled release of drug was achieved from the hydrogels containing the ICs in comparison to the rapid release from hydrogels containing free IBF. The preliminary kinetic analysis emphasized the crucial role of β–CD in the drug release process that influences the polymer relaxation, thereby leading to prolonged release. The cytotoxicity assay validated the hydrogels as non-toxic in nature and hence can be utilized for controlled delivery of IBF.