Semi-interpenetrating Polymer Network Structure Research Articles

A novel route for improving creep resistance of polymers using nanoparticles

In the present work, a one-step approach was suggested for improving creep resistance of thermoplastic polymers using nanoparticles. That is, SiO 2 nanoparticles were pretreated by silane coupling agent to introduce reactive C C double bonds onto their surfaces. Afterwards, in the melt mixing with matrix polypropylene (PP), butyl acrylate monomers reacted with the silane coupling agent on the nanoparticles and then crosslinked to interconnect the particles with each other, while the PP chains penetrated into the networks, forming semi-interpenetrating polymer network (semi-IPN) structure. Taking the advantage of the specific microstructure, the nanoparticles were well distributed in the matrix with enhanced interfacial interaction. As a result, mobility of the matrix molecules was restricted to certain extent, and creep resistance of the nanocomposites became much higher than those of untreated nano-SiO 2/PP system and unfilled PP as well.

Development of chitosan-guar gum semi-interpenetrating polymer network microspheres for controlled release of cefadroxil

Blend microspheres of chitosan (CS) and guar gum (GG) have been prepared using the water-in-oil (w/o) emulsion method. Cefadroxil was loaded into the microspheres and cross-linked with glutaraldehyde, leading to the formation of a semi-interpenetrating polymer network (IPN) structure. The microspheres have been characterized by scanning electron microscopy, X-ray diffraction and differential scanning calorimetry. Scanning electron micrographs showed the formation of non-uniform microspheres with the rough surface. X-ray diffraction and differential scanning calorimetry studies of the plain and the drug-loaded microspheres indicated that drug is dispersed at the molecular level in the semi-IPN matrix. In vitro dissolution experiments performed in pH 7.4 buffer medium indicated a sustained and controlled release of cefadroxil from semi-IPN microspheres up to 10 h. The amount of drug loaded into microspheres, CS-GG composition of the blend and the amount of cross-linking agent used have shown dependencies on the release of cefadroxil from the semi-IPN microspheres.

Introduction of silica into thermo-responsive poly( N-isopropyl acrylamide) hydrogels: A novel approach to improve response rates

The response rates of novel thermo-responsive poly( N-isopropyl acrylamide) (PNIPAM) hybrid hydrogels are compared to those of conventional chemically crosslinked PNIPAM hydrogels. The former materials were obtained by applying the sol–gel technology, in which the inorganic silica particles act as physical crosslinks for the organic polymer chains, leading to a semi-interpenetrating polymer network structure. In situ modulated temperature DSC shows that the introduction of hydrophilic silica improves the thermal response rate of the hybrid hydrogels to a great extent as compared to aqueous PNIPAM solutions and conventional PNIPAM hydrogels. Ex situ gravimetrical measurements also illustrate that the shrinking/swelling rate of the hybrid hydrogels is largely improved. It is assumed that the uniform distribution of the SiO 2 units, as demonstrated by cryo-field emission scanning electron microscopy, causes the silica to act as nano-sized water reservoirs, which reduce the characteristic diffusion length of water in the PNIPAM matrix so that it can be transported faster within the hybrid PNIPAM nano-composite.

Cell viability of chitosan-containing semi-interpenetrated hydrogels based on PCL-PEG-PCL diacrylate macromer

Chitosan-modified biodegradable hydrogels were prepared by UV irradiation of solutions in mild aqueous acidic media of poly(caprolactone)-co-poly(ethylene glycol)-co-poly(caprolactone) diacrylate (PCL-PEG-PCL-DA) and chitosan. Hydrogels obtained were characterized using FT-IR, DSC, TGA and XPS. FT-IR, TGA and DSC revealed the semi-interpenetrating polymer network structure formed in the hydrogel. Though the water swelling degree of these chitosan-modified hydrogels was substantial in the range of 322–539%, it was found that fibroblasts could still attach, spread and grow on them; this is in contrast to the commonly investigated PEG-diacrylate hydrogel. The MTT assay demonstrated that cells could grow better on 3 or 6% chitosan-modified hydrogel than unmodified PCL-PEG-PCL-DA hydrogels or low-content (1%) chitosan-modified PCL-PEG-PCL-DA hydrogel. Increased chitosan content resulted in increased cell interaction and also decreased water swelling, both of which results in increased cell attachment and spread.

Protective coating of lithium metal electrode for interfacial enhancement with gel polymer electrolyte

The polymer electrolyte based on semi-interpenetrating polymer network (IPN) structure for protection was formed on lithium electrode surface by the ultraviolet (UV) radiation-curing method. A curable mixed solution consists of linear polymer (Kynar 2801), a crosslinking agent (1,6-Hexanediol diacrylate), liquid electrolyte (ethylene carbonate (EC)/propylene carbonate (PC)/1 M LiClO 4), and a photoinitiator (methyl benzoylformate). The lithium morphology deposited on the protected lithium electrode was less dendritic and smoother than that on the nonprotected lithium electrode during the 1st charge at 0.25 mAcm −2. The discharge capacity obtained from the unit cell applying the lithium anode protected with gel polymer electrolyte based on semi-IPN [Kynar 2801/1,6-Hexanediol diacrylate, 5/5 (w/w)] was 80% of the initial discharge capacity during 100 cycles at C/2 rate (1.25 mAcm −2).

Water-Resistant Film from Polyurethane/Nitrocellulose Coating to Regenerated Cellulose

Water-resistant films were obtained from polyurethane (PU)/nitrocellulose coating to regenerated cellulose films, which were prepared by coagulating cellulose cuoxam solution. The PU/nitrocellulose coating layer was cured at 80 °C for 2 min and formed semi-interpenetrating polymer networks (semi-IPNs) structure. The tensile strength (σb), water resistivity (R), water vapor permeability (P), and light transmittance of the coated films changed with nitrocellulose content in the coating, and the best values (such as σb, 679 kg·cm-2; R, 53%; P, 0.004 g·cm-2·day-1) were attained at 33 wt % nitrocellulose. The TEM, EPMA, DTA, IR, and UV results showed that the coated films have strong interfacial bonding, which is caused by covalent and hydrogen bonds between the cellulose film and the semi-IPNs coating. The biodegradation half-life t1/2 of the coated films in soil at 20−30 °C was given to be 58 days, and after about 6 months the coated films were almost completely decomposed by microorganisms. SEM and the kine...