Muhammad Bisyrul Hafi Othman

Classification, processing and application of hydrogels: A review.

This article aims to review the literature concerning the choice of selectivity for hydrogels based on classification, application and processing. Super porous hydrogels (SPHs) and superabsorbent polymers (SAPs) represent an innovative category of recent generation highlighted as an ideal mould system for the study of solution-dependent phenomena. Hydrogels, also termed as smart and/or hungry networks, are currently subject of considerable scientific research due to their potential in hi-tech applications in the biomedical, pharmaceutical, biotechnology, bioseparation, biosensor, agriculture, oil recovery and cosmetics fields. Smart hydrogels display a significant physiochemical change in response to small changes in the surroundings. However, such changes are reversible; therefore, the hydrogels are capable of returning to its initial state after a reaction as soon as the trigger is removed.

Thermal properties of polyimide system containing silicone segments

The influence of the structure properties relationships of silicone incorporated polyimide (PI) on thermal stability was investigated by using single scan thermogravimetric analysis (TG) and differential scanning calorimetry (DSC) in nitrogen. Four systems have been synthesized based on monomer 4-(4-(1-(4-(4-aminophenoxy) phenyl)-1-methylethyl) phenoxy) aniline (BAPP)/3,3′,4,4′-Biphenyltetracarboxylic dianhydride including parent PI (S-1), PI siloxane copolymer (S-2 and S-3), and PI siloxane hybrid (S-4). The derivative thermogravimetric analysis (DTG) and DSC curves indicate a double and single stage decomposition process and glass transition temperature (Tg), respectively. While the PI, PIS, and PSH showed distinctive features towards thermal analysis, it was found that the rate of degradation (δα/δt) was influenced by the flexibility of Si–O–Si in the backbone and in Si–O–Si itself. These results revealed that the presence of Si–O–Si in either the backbone or matrix indicates its stability with regard to high thermal service applications.

Functional properties of chitosan built nanohydrogel with enhanced glucose-sensitivity

A new approach to design multifunctional chitosan based nanohydrogel with enhanced glucose sensitivity, stability, drug loading and release profile are reported. Two approaches were followed for functionalization of chitosan based nanohydrogel with 3-APBA via EDC and 3-APTES. The effective functionalization, structure and morphology of Chitosan based IPN respectively were confirmed by FTIR, SEM and AFM. At physiological conditions, the glucose-induced volume phase transition and release profile of the model drug Alizarin Red with 1,2-diol structure (comparative to insulin as a drug as well as a dye for bio separation) were studied at various glucose concentrations, pH and ionic strengths. The results suggested a new concept for diabetes treatment and diols sensitivity in view of their potential hi-tech applications in self-regulated on-off response to the treatment (drug delivery and bio separation concurrently).

Kinetic investigation and lifetime prediction of Cs–NIPAM–MBA-based thermo-responsive hydrogels

This study attempted to clarify the influence of a cross-linker, N,N-methylenebisacrylamide (MBA), and N-isopropylacrylamide (NIPAM) on the non-isothermal kinetic degradation, solid state and lifetime of hydrogels using the Flynn-Wall-Ozawa (F-W-O), Kissinger, and Coats-Redfern (C-Red) methods. The series of dual-responsive Cs-PNIPAM-MBA microgels were synthesized by soapless-emulsion free radical copolymerization in an aqueous medium at 70 °C. The thermal properties were investigated using thermogravimetric analysis (TG) and differential scanning calorimetry (DSC) under nitrogen atmosphere. The apparent activation energy using the chosen Flynn-Wall-Ozawa and Kissinger methods showed that they fitted each other. Meanwhile, the type of solid state mechanism was determined using the Coats-Redfern method proposed for F1 (pure Cs) and F2 (Cs-PNIPAM-MBA hydrogel series) types, which comprise random nucleation with one nucleus reacting on individual particles, and random nucleation with two nuclei reacting on individual particles, respectively. On average, a higher Ea was attributed to the greater cross-linking density of the Cs hydrogel.

Synthesis and physicochemical investigation of chitosan-built hydrogel with induced glucose sensitivity

ABSTRACT There is an urgent need to treat diabetes, and therefore, this work reports on a chitosan-built hydrogel functionalized by a glucose sensing moiety, which simulates pancreatic activity. The effect of external stimuli on various internal properties was investigated to establish the action of the hydrogel. The model drugs, fluorescein (D1) and rhodamine (D2), with a diol architecture, were investigated spectroscopically with 75.94% loading and 65.63% release. Consequently, a ligand to glucose ratio of 2:1 in comparison with a ligand to model drug ratio of 1:1 was addressed. The system was expected to lead to findings on applications for the self-controlled release of insulin in response to blood glucose levels. GRAPHICAL ABSTRACT

Thermal degradation behavior of a flame retardant melamine derivative hyperbranched polyimide with different terminal groups

Melamine derivative hyperbranched polyimide (HPI) polymers with different terminal groups were synthesized by emulsion polymerization reactions, followed by stepwise thermal imidization. The non-isothermal behavior of the synthesized HPI polymers was studied by thermogravimetric analysis under a nitrogen atmosphere and the results were compared with the corresponding terminal groups. In this study, we attempted to clarify the effects of different terminal groups on the non-isothermal degradation kinetics. The derived apparent activation energies using Flynn–Wall–Ozawa and Kissinger methods fit well with each other (showing the same trend). Meanwhile, the type of solid state mechanism was determined using the Coats–Redfern and Criado methods proposed for D1 types such as amine–amine terminals, amine–anhydride terminals and anhydride–anhydride terminals, which are one-dimensional diffusions that follow the unimolecular decay law of first order reactions. The Ea showed significant differences at α > 0.7, which indicates the role of different terminal groups towards degradation behavior. From the calculations, the lifetime prediction at 5% mass loss decreases in the following order: anhydride terminated > amine terminated > anhydride–amine terminated which is related to the dissociation energy between the anhydride functional groups and amine functional groups. Hence, the presence of different terminal groups reveals their contributions towards thermal degradation and stability.

Synthesis and Characterization of Highly Cross-Link Polysiloxane Based on 2,4,6,8- Tetramethyl-2,4,6,8- Tetravinylcyclotetrasiloxane

A series of hydrosilyl-terminated polydimethyl-siloxane (HTP) of different molecular weight was cross-linked with 2,4,6,8-tetramethyl-2,4,6,8-tetravinyl-cyclotetra siloxane (D4V) to afford a three dimension cross-link network. They were systematically synthesised through acid-catalyzed ring opening polymerization of octamethyl-cyclotetrasiloxane (D4) followed by hydrosilylation reaction using Platinum complex catalyst. Chemical structure of HTP was characterized using FTIR and H-NMR. Mechanical properties were established using Shore A hardness which were closely related to the cross-link density.

Synthesis and evaluation on pH- and temperature-responsive chitosan-p(MAA-co-NIPAM) hydrogels

In this study, chitosan-poly(methacrylic acid-co-N-isopropylacrylamide) [chitosan-p(MAA-co-NIPAM)] hydrogels were synthesized by emulsion polymerization. In order to be used as a carrier for drug delivery systems, the hydrogels had to be biocompatible, biodegradable and multi-responsive. The polymerization was performed by copolymerize MAA and NIPAM with chitosan polymer to produce a chitosan-based hydrogel. Due to instability during synthesis and complexity of components to produce the hydrogel, further study at different times of reaction is important to observe the synthesis process, the effect of end product on swelling behaviour and the most important is to find the best way to control the hydrogel synthesis in order to have an optimal swelling behaviour for drug release application. Studied by using Fourier transform infra-red (FTIR) spectroscopy found that, the synthesized was successfully produced stable chitosan-based hydrogel with PNIPAM continuously covered the outer surface of hydrogel which influenced much on the stability during synthesis. The chitosan and PMAA increased the zeta potential of the hydrogel and the chitosan capable to control shrinkage above human body temperature. The chitosan-p(MAA-co-NIPAM) hydrogels also responses to pH and temperature thus improved the ability to performance as a drug carrier.

Synthesis and functionalization of chitosan built hydrogel with induced hydrophilicity for extended release of sparingly soluble drugs

Abstract Addressing the functional biomaterials as next-generation therapeutics, chitosan and alginic acid were copolymerized in the form of chemically crosslinked interpenetrating networks (IPNs). The native hydrogel was functionalized via carbodiimide (EDC), catalyzed coupling of soft ligand (1,2-Ethylenediamine) and hard ligand (4-aminophenol) to replace –OH groups in alginic acid units for extended hydrogel- interfaces with the aqueous and sparingly soluble drug solutions. The chemical structure, Lower solution critical temperature (LCST ≈ 37.88 °C), particle size (Zh,app ≈ 150–200 nm), grain size (160–360 nm), surface roughness (85–250 nm), conductivity (37–74 mv) and zeta potential (16–32 mv) of native and functionalized hydrogel were investigated by using FT-IR, solid state-13C-NMR, TGA, DSC, FESEM, AFM and dynamic light scattering (DLS) measurements. The effective swelling, drug loading (47–78%) and drug release (53–86%) profiles were adjusted based on selective functionalization of hydrophobic IPNs due to electrostatic complexation and extended interactions of hydrophilic ligands with the aqueous and drug solutions. Drug release from the hydrogel matrices with diffusion coefficient n ≈ 0.7 was established by Non- Fickian diffusion mechanism. In vitro degradation trials of the hydrogel with a 20% loss of wet mass in simulated gastric fluid (SGF) and 38% loss of wet mass in simulated intestinal fluid (SIF), were investigated for 400 h through bulk erosion. Consequently, a slower rate of drug loading and release was observed for native hydrogel, due to stronger H-bonding, interlocking and entanglement within the IPNs, which was finely tuned and extended by the induced hydrophilic and functional ligands. In the light of induced hydrophilicity, such functional hydrogel could be highly attractive for extended release of sparingly soluble drugs.