Iranian polymer journal
Volume:20 Issue: 2, 2011

The novel nanocomposite based on poly(carbonate-urea)urethane and polyhedraloligomeric silsesquioxanes (POSS) has been used in medicine especially incardiovascular applications. It is also known that the cell affinity towardsbiomaterials can be promoted by immobilization of extracellular matrix proteins ontothese materials surfaces. The inert surface of POSS-PCU nanocomposite is notdirectly suitable for immobilization of such biomolecules and therefore, its biocompatibilityshould be improved. In this study, design of experiment methodology wasused to develop a predictive model to optimize the operating conditions for graftingcontrolled amounts of carboxylic functional groups onto the surface of POSS-PCU,which may then be used for the coupling of ECM proteins. The grafting of poly(acrylicacid) was carried out using a two-step plasma treatment. The grafted films werecharacterized by ATR-FTIR spectroscopy, SEM, and water contact angle measurements.The presence of the grafted layers was confirmed by the appearance of a broadpeak of the hydroxyl groups in ATR-FTIR spectrum, decreased in water contact angle,and morphological changes observed by SEM micrographs. The effects of twoidentified process variables (pretreatment and copolymerization time length) each infive levels, on the grafting density were investigated and optimized using centralcomposite design in the response surface methodology. The accuracy of the modelwas verified and found to be high. In process optimization, it was found that themaximum value of grafting density was 13.9 (± 28) μg/cm2, by using the appropriatevalues of process variables which were achieved through the experimental conditionsof 75 s and 120 s for pretreatment time and copolymerization time, respectively

The changes in the crystalline structure of polyvinylidene fluoride (PVDF) wereinvestigated via preparation of its blends with polymethyl methacrylate (PMMA),polyethylene terephthalate (PET) and polyvinyl chloride (PVC) in molten states inan internal mixer at 10% to 40 wt% of the last two polymers. In all the blends, anincrease in β-crystal content of PVDF was observed at different degrees and differentmorphologies. Polyvinylidene fluoride blends with PMMA showed a homogeneousmorphology, whereas those with PET and PVC showed two-phase morphologies.These were accounted for the solubility parameter differences of the polymers. In thecase of PVC the mismatch of processing conditions was found to be the main reasonfor the observed morphology. The technique of FTIR spectroscopy revealed that therelative β-crystal content of PMMA blend reached 70% at 30 wt% PMMA, whereas PETand PVC achieved 80% β-crystals by only 10 wt% modification. This was attributed tothe interactions of the blended polymers with PVDF molecules in amorphous regionsor at their interphases. The effects of PVC and PET on the beta-crystal content of PVDFare similar although the blends in the case of PET produce finer morphology as comparedwith those of PVC. It is desirable to find and maximize the content of PVDF infinal piezoelectric article. The technique of WXRD shows limited changes in shape andposition of PVDF/PMMA and PVDF/PVC blends spectra and considerable changes inshape of PVDF/PET blends spectra. This is found to be related to the amorphous andsemi-crystalline structures of PVC and PET, respectively. Due to the sphericalsymmetry of the PVDF spherulites the piezoelectric coefficient of the blends are foundto be zero.

Chitosan is the product of N-deacetylation of chitin. For its innocuous, renewable,biocompatible property chitosan is applied in many fields e.g., pharmaceutical,food, catalysis, material. In this work, three chitosan-based Schiff-based (CSB)compounds with aromatic substituent groups were synthesized from the reaction ofchitosan with different aromatic aldehydes i.e., salicylaldehyde, 4-hexadecyloxy-2-hydroxybenzaldehyde and 2-hydroxy-1-naphthaldehyde. The chitosan-based Schiffbase copper (II) complexes (CSBCu) were subsequently obtained through the reactionof relative Schiff bases with copper acetate. These products were characterized byelementary analysis (EA), Fourier transform infrared (FTIR) spectroscopy, thermalanalysis (TG-DSC, TG-DTA), and X-ray diffraction (XRD) spectra, respectively.Generally, elemental analysis data may confirm the formation of chitosan-Schiff baseas well as the coordination reaction of CSB with copper ions. FTIR analysis indicatedthat Schiff base and coordination reaction take place in Schiff base skeleton. Moreover,with the difference in substituent groups and spacer, FTIR spectra showed the clearvariety. Thermal analysis showed that the thermal stability of CSB increased slightly,while that of the copper complexes was reduced significantly in comparison withchitosan. The XRD results demonstrated the appearance of a new crystallization peakof CSB in the vicinity of five degree and the lower crystallinity of CSBCu. Thedifferences in crystallinity and thermal stability are mainly attributed to the formation ofSchiff base group and complexation with copper ions, as well as spatially partialhindrance and hydrophobic forces in the aromatic substituent groups. The presentresults show that the specific properties of chitosan-based Schiff base derivatives canbe altered by modifying the molecular structures of objective compounds with propersubstituent groups.

Rubber modification of styrene/acrylonitrile (SAN) copolymer has been carriedout using acrylonitrile/styrene/acrylate (ASA) structural rubber latex copolymerparticles with a rubbery acrylate core and a rigid SAN (30 wt% acrylonitrile, AN)graft shell. The melt flow and toughness of SAN copolymer have been investigated inrelation to core composition and particle morphology. The results showed that incorporationof rubber particles increases the torque equilibrium of the SAN copolymer duringthe melt blending process. The lowest and highest torque values were obtained for theblend samples containing large core-shell and small hemispheric rubber particles,respectively. On the other hand, the highest impact toughness was observed for theblend sample containing ASA core-shell structured particles with P(BA-co-2EHA) corecomposition due to its lowest glass-rubber transition temperature (Tg). The TEM micrographswere indications of good dispersibility for the particles with raspberry and coreshellstructures within the SAN matrix. Whereas, large particle agglomerates wereobserved for the blends containing hemispheric structural particles. Dynamic mechanicalthermal analysis (DMTA) results showed that the blends with core-shell particlespossess a higher maximum tan δ and lower tan δ-curve broadening when compared toblends containing rubber particles with other morphologies. A good dispersion state ofcore-shell rubber particles in the copolymer matrix resulted in a more homogeneousstructure and a narrower tan δ curve.

The objective of the present work was to synthesize the novel hybrid basedpolymeric networks of pectin and acrylic acid (AA) showing pH-sensitive swellingperformance in relation to acrylic acid component of the gel. A series ofhydrogels were prepared using pectin and acrylic acid (AA) in the presence of N,Nmethylenebisacrylamide (MBAAm) as cross-linker and benzoyl peroxide asinitiator. FTIR confirms the formation of network. The prepared hydrogels wereevaluated for swelling, sol-gel fraction and porosity. Furthermore, the values ofequilibrium water content (EWC), diffusion coefficient (D) and volume fraction of thepolymer within hydrogels (Φ2) were calculated. Hydrogels were characterized forsurface morphology using scanning electron microscopy (SEM). Swelling data werefitted into Peppas model for evaluating the swelling mechanism. Hydrogels showed pHand monomeric composition-dependent swelling behaviour. Selected samples wereloaded with verapamil as a model drug. Drug release was performed in USP phosphatebuffers of pH 1.2 and 7.5. Drug release data were fitted into various kinetic models likezero order, first order, Higuchi and Peppas models for investigating the optimumcomposition suitable for controlled drug delivery. A significant difference in drugrelease kinetics was observed by varying the composition of pectin/AA and degree ofcross-linking.

Three aromatic bismaleimide resins, 4,4′-bismaleimidodiphenyl methane (BMIDDM),4,4′-bismaleimidodiphenylether (BMIDDE) and 4,4′-bismaleimidodiphenylsulphone (BMIDDS) having various bridging groups from the correspondingamine monomers (4,4′-diaminodiphenylmethane (DDM), 4,4′-diaminodiphenylether(DDE) and 4,4′-diaminodiphenylsulphone (DDS)) were prepared. These resins werecharacterized by FTIR and NMR spectroscopy techniques. BMIDDM/BMIDDE andBMIDDM/BMIDDS mixtures at various concentrations were prepared to study thebismaleimide resin eutectic mixtures. Differential scanning calorimetry analysis wasused to demonstrate the phase diagrams, the melting and solubility of each constituentof these binary systems (BMIDDM/BMIDDE and BMIDDM/BMIDDS) in different liquidand solid phases. Furthermore, in the present work the relationship between binarysystems and the concept of a eutectic mixture with its extraordinary thermal propertiesis investigated. The eutectic melting point of the BMIDDM/BMIDDS system isconsiderable because of the much lower melting point of the above system comparedto that of the synthesized monomer having the lowest melting point. It shows also avery easy way of using these materials in the molten state. The same DSC study onother mixtures, i.e., BMIDDM/BMIDDE and BMIDDE/BMIDDS is performed and theresults are reported. The end results illustrate that by increasing the quantity of onemonomer in the mixture, two melting points appear until they acquire the meltingtemperature of the eutectic composition (Te, a single and homogeneous peak).Impurities have similar effects on To and Texo. The findings of this work can beapplicable in the transportation industry, particularly in areas such as civil and militaryaircraft industry, aerospace, marine and automotive sectors.