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The electrospray deposition method was used to deposit carbon nanotubes (CNT) onto the surfaces of woven carbon fiber (CF) to produce woven hybrid carbon fiber–carbon nanotubes (CF–CNT). Extreme high-resolution field emission scanning electron microscopy (XHR-FESEM), X-ray diffraction (XRD), Raman spectroscopy and Fourier transform infrared spectroscopy (FT-IR) were used to analyze the woven hybrid CF–CNT. The results demonstrated that CNT was successfully and homogenously distributed on the woven CF surface. Woven hybrid CF–CNT epoxy composite laminates were then prepared and compared with woven CF epoxy composite laminates in terms of their flexural and dielectric properties. The results indicated that the flexural strength, flexural modulus and dielectric constant of the woven hybrid CF–CNT epoxy composite laminates were improved up to 19, 27 and 25%, respectively, compared with the woven CF epoxy composite laminates.

A study was carried out to determine the effectiveness of lignin, extracted from oil palm (Elaeis guineensis) biomass as water-in-oil (W/O) emulsifying agent. To achieve this goal, soda lignin (SL) was extracted via soda pulping process and a series of nanosized soda lignin (NSL) were prepared using homogenizer at three different speed i.e. 10,400 rpm (NSL 10), 11,400 rpm (NSL 11) and 12,400 rpm (NSL 12) for one hour. All prepared samples were characterized by FT-IR, UV–Vis spectroscopy, thermogravimetric analysis (TGA), zeta potential analyser, Transmission Electron Microscope (TEM) and Extreme High Resolution Field Emission Scanning Electron Microscope (XHR-FESEM). The result of FTIR showed that there is no prominent change occurred in spectra of all samples while a good stability was reflected by TGA curves. The percentage of creaming index and visual observations of all samples demonstrated that NSL 12 and dosage 2 g (out of 1 g, 1.5 g and 2 g) were found to be the best among all samples. Furthermore, the results of IFT indicate that NSL 12 was proven to be more stable than the commercial product. Therefore, NSL 12 is selected for toxicological studies and was found safe in both, in vitro and in vivo studies.

Hydrazine borane (HB) is a chemical hydrogen storage material with high gravimetric hydrogen density of 15.4 wt%, containing both protic and hydridic hydrogen. However, its limitation is the formation of unfavorable gaseous by-products, such as hydrazine (N2H4) and ammonia (NH3), which are poisons to fuel cell catalyst, upon pyrolysis. Previous studies proved that confinement of ammonia borane (AB) greatly improved the dehydrogenation kinetics and thermodynamics. They function by reducing the particle size of AB and establishing bonds between silica functional groups and AB molecules. In current study, we employed the same strategy using MCM-41 and silica aerogel to investigate the effect of nanosizing towards the hydrogen storage properties of HB. Different loading of HB to the porous supports were investigated and optimized. The optimized loading of HB in MCM-41 and silica aerogel was 1:1 and 0.25:1, respectively. Both confined samples demonstrated great suppression of melting induced sample foaming. However, by-products formation was enhanced over dehydrogenation in an open system decomposition owing to the presence of extensive Si-O···BH3(HB) coordination that further promote the B-N bond cleavage to release N2H4. The Si-OH···N(N2H4) hydrogen bonding may further promote N-N bond cleavage in the resulting N2H4, facilitating the formation of NH3. As temperature increases, the remaining N-N-B oligomeric chains in the porous silica, which are lacking the long-range structure may further undergo intramolecular B-N or N-N cleavage to release substantial amount of N2H4 or NH3. Besides open system decomposition, we also reported a closed system decomposition where complete utilization of the N-H from the released N2H4 and NH3 in the secondary reaction can be achieved, releasing mainly hydrogen upon being heated up to high temperatures. Nanosizing of HB particles via PMMA encapsulation was also attempted. Despite the ester functional group that may favor multiple coordination with HB molecules, these interactions did not impart significant change towards the decomposition of HB selectively towards dehydrogenation.

Over the last decade, nickel nanoparticles (NiNPs) have been investigated for various potential applications due to their superior ferromagnetic properties such as magneto-crystalline anisotropy, high coercive forces, and chemical stability. Therefore, there has been a tremendous enhancement in the synthesis techniques, proposed reaction mechanisms, and applications of NiNPs. This paper presents a recent overview of the synthesis, reaction mechanisms, and applications of NiNPs. NiNPs in the size range of 1–100 nm are synthesized by various methods for research and commercial applications. The synthesis techniques are classified into three main types, namely, top-down, bottom-up, and hybrids of top-down and bottom-up protocols including solvothermal, physical, and chemical approaches. The detailed reaction mechanisms in the formation of NiNPs, especially for biosynthesis techniques, are extensively described. Trends in NiNP applications in fields such as biomedical, catalysis, supercapacitors, and dye-sensitized solar cells are explored. The basic advantages and role of NiNPs as a catalyst for various reactions are illustrated here.

The effect of the polymeric cross-link density on the thermal conductivity of an oxidized graphene (OG)-filled epoxy nanocomposite was investigated by two different fabrication methods, namely a conventional OG mixing (OGconventional) and a diamine–colloidized OG (OGcolloidized) method. Epoxy composites with 3 wt% OG were prepared via the diamine–OG fabrication method to produce an epoxy nanocomposite with a higher cross-link density than that of an epoxy composite with also 3 wt% of OG prepared via the conventional fabrication method. The cross-link densities of the epoxy nanocomposites were calculated by means of a solvent swelling test. The epoxy/OGcolloidized nanocomposite showed a higher cross-link density and higher thermal conductivity than the epoxy/OGconventional nanocomposite with the same filler concentration. It was observed that for the epoxy/OGcolloidized nanocomposite, where an amide network was relatively formed between the carboxylic and amine groups, a high cross-link density enhanced the thermal conductivity by means of the transport of phonons. Furthermore, high dispersion of OG gives high dielectric constant to epoxy/OGcolloidized even having the same amount of graphene loading.

In this paper, a highly chemical stable 4,4′,4″-((1,3,5-triazine-2,4,6-triyl)tris(oxy))trianiline (TTA) was successfully synthesized with 4,4′-(4,4′-Isopropylidene-diphenoxy)bis(phthalic anhydride) (BPADA) using direct nucleophilic addition in Dimethylformamide (DMF). The resulting Hyperbranched Polyimide (HPI) was characterized by means of conventional methods such as Fourier transform infra-red (FT-IR) and proton nuclear magnetic resonance (1H NMR) spectroscopy, gel permeation chromatography (GPC), solubility tests, Field Emission Scanning Electron Microscopy (FESEM), Electron Diffraction X-ray analysis (EDX), Vickers hardness test, thermogravimetric analysis (TG), differential scanning calorimetry (DSC), and thermal conductivity. High molecular weight was obtained by extending the reaction time for 2 h. The TTA/BPADA HPI demonstrated a high chemical stability and could be readily used in the precursor state. The thermal curing led to an increase of the imidization degree and greatly improved the thermal stability (Tg above 200 °C, maximum mass loss >500 °C and char yield >55%), due to an increasing chain packing density). Therefore, it is believed that this incorporated HPI structure containing s-triazine moieties in a polyimide system shows potential as a new high performance and highly functional material. Keywords: Hyperbranched polyimide (HPI), S-triazine ring, Degree of imidization, Thermally stable, Highly chemical stable

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.

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.

Star-shaped self-assembled micelles of block copolymer chitosan-co-poly(ethylene glycol) methyl ether methacrylate hydrogel were successfully synthesized by free-radical copolymerization and were investigated against Fluorescein as an anticancer hydrophobic model drug. The chemical structures of synthesized hydrogel were characterized by FT-IR, TGA, DSC, FESEM, AFM, and their interfaces in water, Fluorescein, salt, and urea were studied using dynamic light scattering (DLS) technique. The self-assembled blank and fluorescein-loaded micelles with an average size (z average ≈ 50–350 nm), critical micelle concentration (CMC ≈ 2.90 mg L−1), maximum stability (zeta potential ≈ 30 mV), electrophoric mobility ≈ 22 mV, conductivity ≈ 250 mV, and lower critical solution temperature (LCST ≈ 38.80 °C) were explored. The in vitro studies revealed 78% loading and 66% release profiles. The DLS and drug administration profiles suggested the system as hydrophobic anticancer drug carrier at physiological conditions.

A different sequence of epoxy composite preparation was performed by mixing oxidized graphene platelets (oGNP) with a curing agent prior to mixing it with epoxy resin. When oGNP was mixed with trimethylhexamethylene diamine (TMD), the condensation reaction between the hydroxyl and amine groups resulted in the formation of a TMD/oGNP colloid. The TMD/oGNP colloid was used to cure epoxy resin. The colloidization eventually improved the dispersion and prevented re-agglomeration in the epoxy resin. A thermogravimetric analysis showed that the thermal stability of the epoxy/oGNP system had improved, while the presence of the oGNP gave more stability to the solvent in terms of an increase in the crosslink density. These results showed that the TMD/oGNP colloid sequence was better able to enhance the properties of the epoxy composite compared to the conventional method of obtaining epoxy/graphene by mixing the graphene with the epoxy resin prior to adding in the curing agent.

The multi-scale hybridisation of carbon nanotube (CNT) and alumina (Al 2 O 3 ) was synthesised by using chemical vapour deposition. The idea of hybridisation between the CNT and Al 2 O 3 particles is to prevent the agglomeration of the CNT due to van der Waals attractions. The Al 2 O 3 particles work as “vehicles” for the CNTs to disperse homogenously in the epoxy matrix and improve the particle/matrix interface. Epoxy composites with the CNT–Al 2 O 3 hybrid compound were observed to exhibit an enhancement of 117% and 148% in compressive strength and compressive modulus, respectively. Similarly, thermal stability improvement has also been observed for the CNT–Al 2 O 3 hybrid compound epoxy composite system.

This paper presents a multi-scale hybridization of carbon nanotube (CNT) with clay in polymers, which offers improvement in the mechanical properties of the composites. In this study, hybrid filler, comprised of CNT grown directly on muscovite particles by chemical vapour deposition using methane as the carbon precursor, is prepared. This CNT–Muscovite Hybrid compound is incorporated into the epoxy matrix at various filler loadings (1–5 wt.%) and compared with physically mixed CNT–Muscovite. The tensile strength, tensile modulus, and micro-hardness of Epoxy/CNT–MUS HYB nanocomposites are determine to exhibit an improvement of up to 86.58%, 134.59% and 14%, respectively, compared to neat epoxy. These improvements are mainly attributed to by the good dispersion of CNT–Muscovite Hybrid in the epoxy composites. Keywords: Polymer composites, Nanocomposites, Multiwalled carbon nanotubes, Chemical vapour deposition

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.

Recent technological advances demanded incorporation of SiOSi segment into polyimides (PI)s to improve versatility in terms of processing, morphology and optoelectronic properties. In order to study the role of SiOSi segment in the morphology and hardness properties of PI, the SiOSi segment have been introduced into the PI backbone through the conventional copolymerization and in PI matrix through sol gel method. The PI series were characterized by Fourier transform infra-red (FT-IR), nuclear magnetic resonance (NMR) spectroscopy, elemental analysis, solution viscosity and gel permeation chromatography (GPC). Scanning electron microscope (SEM) analysis suggested a microphase separation between the two components. FT-IR spectra confirmed the presence of silicone segment, as well as a complete imidization of PI series. Micrograph suggested a homogeneous phase between the PI and silicone segment for copolymerization series while sol gel technique revealed the inorganic particles were distributed homogenously in PI matrix. It was also found that the presence SiOSi segment in PI backbone and PI matrix influenced the opto-electronic properties. Keywords: Polyimide (PI), Silicone segment, Morphology, Hardness, Optoelectronic properties

The effects of hybrid filler of zinc oxide and chitosan (chitosan–ZnO) on thermal, flexural, antimicrobial, chemical resistance, and hardness properties of ultrahigh-molecular-weight polyethylene (UHMWPE) composites with varying concentration of zinc oxide (ZnO) and further hybridized by chitosan (CS) were successfully studied. The composites were prepared using mechanical ball milling and followed by hot compression molding. The addition of ZnO to the UHMWPE matrix had lowered the melting temperature (Tm) of the composite but delayed its degradation temperature. Further investigation of dual filler incorporation was done by the addition of chitosan to the UHMWPE/ZnO composite and resulted in the reduction of UHMWPE crystallization. The flexural strength and modulus had a notably high improvement through ZnO addition up to 25 wt% as compared to neat UHMWPE. However, the addition of chitosan had resulted in lower flexural strength than that of 12 wt% ZnO UHMWPE composite but still higher than that of neat UHMWPE. It was experimentally proven that the incorporation of ZnO and chitosan particles within UHMWPE matrix had further enhanced the antimicrobial properties of neat UHMWPE. Chemical resistance was improved with higher ZnO content with a slight reduction of mass change after the incorporation of chitosan. The hardness value increased with ZnO addition but higher incorporation of chitosan had lowered the hardness value. These findings have significant implications for the commercial application of UHMWPE based products. It appears that these hybrid fillers (chitosan–ZnO)-reinforced UHMWPE composites exhibit superior overall properties than that of conventional neat UHMWPE. POLYM. COMPOS., 2015. © 2015 Society of Plastics Engineers

We has synthesized hyperbranched polyamides (HPI) series containing s-triazine rings derived from melamine in the main chain, according to A3 + B2 approach which involving the emulsion polymerization reactions of melamine in hydrochloric acid and stepwise thermal imidization. The effect of curing temperature on the degree of imidization (DI) films of Melamine-BPADA (4,4'-(4,4'-Isopropylidenediphenoxy) bis (phthalic anhydride) has been examined by using the techniques of FTIR (Fourier transform infrared) and SEM-EDX (Scanning Electron Microscope-Electron Diffaction X-Ray). The DI varied significantly with annealing temperature before the films were fully cured. The Melamine-BPADA film was nearly fully cured when annealed at 180 °C, while the same was revealed for SEM-EDX. The morphology of the Melamine-BPADA film did not vary with annealing at temperatures and the FTIR experiment fairly match those from the SEM-EDX.

The influence of cross-linker (N,N-methylenebisacrylamide, MBA) and methacrylic acid (MAA) composition on the thermal stability, degradation kinetic, and lifetime, of Chitosan-based [Chitosan-poly(methacrylic acid, (Cs-PMAA)] dual responsive hydrogels was investigated in detail using the Flynn–Wall–Ozawa (F–W–O) method. The Cs-MAA–MBA derivatives showed only a glass transition temperature (Tg) that increased as the content of MAA increased. The stability of Cs-MAA–MBA has been achieved at a critical point where the MAA content was 300 mg/ml and MBA was 15 mg/ml. The lifetime of Cs-PMAA hydrogels (time at 5% mass loss) was estimated by increased temperature delivery in nitrogen atmosphere. On average, a higher Ea has been attributed to the greater cross-linking density of Cs hydrogel. Likewise, the lower swelling ability of Cs hydrogel can be due to the slower relaxation rate of the polymer chain, which then results in an increased lifetime of the potential drug-release rate.

This study describes the synthesis, characterization and detailed physicochemical investigation on the stimuli-responsive behaviour of chitosan-poly (N-isopropylacrylamide) [chitosan-PNIPAM] copolymer microgels. Six different compositions of dual-responsive chitosan-PNIPAM based microgels were synthesized by soapless-emulsion free radical copolymerization method in an aqueous medium at 70 °C. The chemical composition, swelling/de-swelling, volume phase transitions, electrical properties, colloidal stability, and physicochemical behaviour under various pH/temperature conditions were investigated using Fourier transform infrared spectroscopy (FTIR), dynamic light scattering (DLS), zeta-potential, and rheology. Various functional groups present in the copolymer microgels were confirmed by FTIR analysis. The hydrodynamic diameter (D h), volume phase transition temperature (VPTT), and swelling/de-swelling behaviour of microgels, under different pH and temperature conditions, in aqueous media were investigated using DLS measurements. Zeta potential measurements were used to evaluate the stability, electrical and electro-kinetic properties of the gels at various pH/temperatures. Likewise, the influence of temperature and chemical composition of microgels on the particle behaviour was investigated through rheological studies. A transition from sol-to-gel state at temperature beyond 50 °C was also noticed in all hydrogel samples. On the basis of results obtained, we observed that variables such as NIPAM/chitosan ratio, amount of cross-linker, and temperature/pH not only affect the above mentioned properties but also affect the dual-sensitivity and stability of the microgels. Most of the chitosan-PNIPAM particles remained soluble and maintained good stability without significant sedimentation in water through a wide range of pH (pH ≈ 2–8) for about 3 months at room temperature.

The synthesis of hyperbranched polyamide (HPI) series containing s-triazine rings derived from melamine in the main chain took place according to an A3 + B2 approach, which entailed a conventional two-step method involving the emulsion polymerisation reactions of melamine in hydrochloric acid and stepwise thermal imidisation. The resulting HPIs were characterised by FT-IR and 1H-NMR spectroscopy, gel permeation chromatography, solubility tests, thermogravimetric analysis and differential scanning calorimetry. The influences of monomer feed ratio, reaction medium concentrations and reaction temperature were studied to find the optimal synthesis conditions. The HPI had imidised more than 88 % at 180 °C, narrow molecular weight distribution in the range of 1.21–1.28, soluble in polar aprotic solvent, and thermally stable up to 450 °C (except MB11HT and MB11HV) with glass transition temperature (T g) around 192 °C. The excess feeding, either A3 or B2, determined the terminal group, while extending the reaction temperature decreased the yield of the product.

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.

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.

This study examines the effects of different types of salt fillers and salt filler loadings on anionic polyacrylamide (A-PAM). Urea, potassium chloride, sodium chloride, and sodium sulfate were incorporated into the A-PAM solution with 10, 20, and 30 wt.% loadings. The characteristics of the A-PAM solution were measured based on the dissolution rate, viscosity, ζ potential, turbidity reduction and floc size. The introduction of salt fillers increased the dissolution rate and reduced the viscosity based on the electrolyte strength of the salt fillers. Stronger electrolytes showed an increased dissolution rate, decreased viscosity, increased turbidity reduction, and decreased floc size. Stronger electrolytes also showed fluctuating and uneven values in the ζ (zeta) potential due to the uneven placement of ions in the A-PAM solution system. The urea-filled A-PAM showed a ζ potential trend similar to that of the unfilled A-PAM. It can be concluded that the strength of ion dissociation plays an important role in the dissolution rate, viscosity, and flocculation characteristics of a salt-filled A-PAM solution.

Crosslink density is one of the factors which dictate the optical and mechanical properties of silicone-based polymers. A series of hydrosilyl-terminated polydimethylsiloxane cured with 2,4,6,8-tetramethyl-2,4,6,8-tetravinyl cyclotetrasiloxane was prepared to form a crosslink network. They were clear gel forms whose elastomeric features were dependent on the endcapper concentration,1,1,3,3-tetramethyldisiloxane,employed during theirsynthesis. The siloxane-based polymers displayed excellent thermal stability whose decomposition temperature was around 480 ◦ C. The refractive index was in the range 1.410‐1.425.Itwasfoundthattherefractiveindexisdependentonthecrosslinkdensityofthenetwork.Theeffectoffractional freevolumeand‘densification’ofthenetworkwaselucidatedandfoundtocontributetothisdependence.TheLorentz‐Lorenz model was used to integrate these observations. c � 2012 Society of Chemical Industry

A series of highly cross-linked polysiloxane was synthesised via hydrosilylation and condensation reaction. Structural identification using Fourier Transform Infrared (FTIR) and 1 H-NMR confirmed their chemical structures. Their thermal and, mechanical properties, and crystallinity, were analysed and related to the level of cross-link density. These systems displayed elevated thermal and hardness properties at an increased cross-link density. Furthermore, the level of crystallinity was reduced as displayed by XRD analysis. Along with this observation, the calculated fractional free volume (FFV) showed a decreasing trend leading to the ‘ densification ’ effect. It was envisaged that the linear polysiloxane chain segments aligned parallel to each other in a triclinic crystal system to generate a crystalline domain. The spacing between these stacking chains was found to be about 7.2 A as measured from simulated XRD pattern.

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.

Recent technological advances demanded polyimides of improved versatility in terms of electronic, optical and thermal properties. In this work, a series of poly(siloxane–imide) block copolymers were synthesized in order to investigate the effect on their optical and electronic properties. The polyimide unit was derived from 3,3′,4,4′-Biphenyltetracarboxylic dianhydride (BPDA) and 4-(4-{1-[4-(4-aminophenoxy) phenyl]-1-methylethyl} phenoxy) aniline (BAPP) while the siloxane unit was derived from 3-[3-(3-aminopropyl)-1,1,3,3-tetramethyldisiloxanyl] propylamine (DMS) and Poly(dimethylsiloxane), bis(3-aminopropyl)terminated (PDMS). The structure of the polyimide was characterized by fourier transformer infra red (FT-IR), nuclear magnetic resonance (NMR) spectroscopy, elemental analysis, solution viscosity and gas permeation chromatography (GPC). Scanning electron microscope (SEM) analysis suggested a microphase separation between the two components. The refractive index and dielectric properties showed a decreasing trend with increased silicone unit in the polyimide backbone. However ultra violet visible (UV–Vis) and optical transparency was not significantly affected. Electronic and optical properties of this copolymer were discussed in relation to the polysiloxane content.

The trend toward miniaturization in inte- grated circuit fabrication demands good interlayer dielec- tric materials. This need can be met by polyimide (PI), which has extreme thermal and chemical stability and, most importantly, a low dielectric constant. Four porous PIs with symmetrically substituted fluorine contents were synthesized. Different porosity levels were achieved with a sol-gel technique through the incorporation of 10 or 20% tetraethyl orthosilicate into the polymer matrix and then acid etching. Their dielectric constants were correlated with the fluorine contents and porosity levels. High poros- ity levels and higher fluorine contents induced substantial decreases in the PI dielectric constants (2.4-2.7). The re- sultant values were within the applicable range for dielec- tric materials in integrated circuits. V C 2011 Wiley Periodicals, Inc. J Appl Polym Sci 121: 3192-3200, 2011

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.

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.

Chitosan-based (chitosan-poly(methacrylic acid)) responsive hydrogels were synthesized using different gel compositions and at various pH values and temperatures in an aqueous medium, and the physicochemical properties (swelling/de-swelling, electrical properties, colloidal stability, and volume phase transitions) of these hydrogels were investigated. Chitosan-PMAA hydrogels with different compositions were synthesized using the free-radical copolymerization method in an aqueous medium at 70 °C. The synthesized microgels were characterized by Fourier transform infrared spectroscopy (FTIR), dynamic light scattering (DLS), and based on their zeta potentials. FTIR was used to determine the chemical structure of the copolymer hydrogel. DLS was employed to measure the hydrodynamic diameters of the microgels in water at different pH values and temperatures. The electrokinetic properties of the gel were investigated using the zeta potential. The equilibrium swelling/shrinking ratios and the volume phase changes (induced by pH and temperature variations) of the microgels were found to be composition-dependent. Most of the properties of the microgels changed with variations in the physicochemical conditions of the medium used. It was found that the swelling ratios of the microgels increased with pH. An increase in the size of the microgels with temperature was also observed. A clear transition from sol to gel behavior with increasing temperature above 55 °C was also noted.