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The morphology, mechanical, thermal, thermo-mechanical, and flammability properties of Na-ionomer/PPS blends were investigated. FESEM study revealed a transition from a homogeneous structure in pure Na-ionomer to a biphasic sea-island morphology at 20% PPS and a co-continuous micro-fibrous structure at 30% PPS and above. Both tensile and flexural modulus were improved substantially at higher PPS loadings (above 30 wt%). Thermogravimetric analysis and differential scanning calorimetry showed that increasing PPS content improved the thermal stability and altered the crystallization behavior of the blends, with maximum thermal stability observed at 50% PPS. Dynamic mechanical analysis demonstrates increased stiffness and elastic properties in the blends as PPS content was increased, particularly at higher temperatures. Additionally, flame resistance was improved with PPS concentration due to the formation of a protective char layer. These findings suggest that Na-ionomer/PPS blends with higher PPS content are suitable for high-performance applications requiring enhanced mechanical, thermal, thermo-mechanical, and flame-resistant properties. [ABSTRACT FROM AUTHOR]

Highlights In the present work, the tribological as well as thermo‐mechanical properties of glass‐filled and carbon‐filled PTFE composites are investigated. Solid lubricants like molybdenum disulfide (MoS2) and graphite are also incorporated in such composites in order to achieve better friction and wear properties. When compared to virgin PTFE, both carbon‐filled PTFE and glass‐filled PTFE composites showed the lowest wear rate. Again, the specific wear rate of glass‐filled PTFE composite was lower as compared to carbon‐filled PTFE composite sample under all test speed. A novel combination of a reinforcing filler (glass fibers) and a solid lubricant (MoS2) incorporated PTFE composite sample [PTFE (90 wt%) + glass fibers (5 wt%) + MoS2(5 wt%)] exhibited the lowest wear rate of the order of 10−9 mm3/Nm which was reduced to around 100‐fold as compared to virgin PTFE under sliding speed of 6.28 m/s. The wear rate was reduced due to the reinforcement of fibers but fibers support the load preferentially, whereas MoS2 and graphite offers a good lubricating effect. The morphological, thermo‐physical and thermo‐mechanical characterization of such composite materials were also carried out using various techniques such as SEM, TGA, DSC, TMA, and DMTA. Such PTFE composites having very good thermo‐mechanical as well as tribological properties have potential to be used as seals, gears, bearings etc. in dynamic aerospace applications. This investigation relates to the PTFE composites to obtain good thermo‐mechanical as well as tribological properties Incorporation of a novel combination of glass fibers and MoS2 exhibited lowest wear rate of the order of 10−9 mm3/Nm The wear property was around 100‐fold lower as compared to virgin PTFE. Such PTFE composites could be used as seals, gears, bearings etc. in dynamic aerospace applications. [ABSTRACT FROM AUTHOR]

We report the development of novel self‐healing binary thermoplastic elastomeric blends of Zn2+‐neutralized poly[ethylene‐co‐(methacrylic acid)] (Zn‐ionomer) and styrene–butadiene–styrene block copolymer (SBS). Zn‐ionomer/SBS blends were prepared by the melt‐blending technique using a twin‐screw extruder with three mass ratios of 75/25, 50/50 and 25/75. Structure, phase morphology and thermal as well as tensile properties of the samples were characterized. Fourier transform infrared spectroscopy results indicated the presence of two types of polymeric materials and their interactions. Scanning electron microscopy images confirmed the miscibility of blend components which remarkably influenced the properties of the blends. The optimum peak degradation temperature of Zn‐ionomer/SBS (75/25 wt%) blend was observed to be 484 °C. The ratio of the tensile strength of the healed specimens to that of the original specimens was implemented to quantitatively evaluate the self‐healing efficiency of the materials. The self‐healing efficiencies were calculated to be 55.42%, 58.36% and 60.75% for Zn‐ionomer samples healed for 4, 8 and 16 h, respectively. All of the blend samples exhibited self‐healing behavior and the self‐healing efficiency was more than that of virgin Zn‐ionomer which may be credited to the high mobility of SBS segments in the blends. The healing efficiency was increased with an increase of SBS content in the blends and also heat energy facilitated the healing process. The self‐healing efficiencies of Zn‐ionomer/SBS (25/75 wt%) blend sample were calculated to be 75.09%, 80.27% and 80.87%, respectively, for 4, 8 and 16 h of healing time at 100 °C. A comparison of optical micrographs of the cut area of samples (before healing and after the healing process) was also made and self‐healing of the blend materials was observed. © 2023 Society of Industrial Chemistry. [ABSTRACT FROM AUTHOR]

Poly(N-isopropyl acrylamide-co-disperse yellow 7 methacrylate) (PNIPAM) copolymers were synthesized by radical polymerization of N-isopropyl acrylamide with disperse yellow 7 methacrylate using 2,2/-Azo-bis-isobutyronitrile (AIBN) as an initiator. N-isopropyl acrylamide is a thermoresponsive monomer, and disperse yellow 7 methacrylate is a photoactive monomer. The synthesized photoactive and thermoresponsive copolymers were characterized by FTIR, NMR, and UV-Vis spectrophotometer with a temperature variation. A proton NMR signal at 8.16 ppm is observed for aromatic protons surrounded by an azo (-N=N-) group. The peak that appeared at 4.0 ppm is due to the CH-CONH group. The amide group proton of CONH appeared at 8.16 ppm. The molecular weights of homopolymers (like PNIPAM and PDY7MA) and their copolymers (PNIPDY) were observed to be 104 and 103 Da, respectively. The optical band gaps for synthesized copolymers, PNIPDY-1B, PNIPDY-2B, and PNIPDY-3B, are 2.98 eV, 2.95 eV, and 2.91 eV, respectively. The multiple emission spectra were observed at 407 nm, 428 nm, and 460 nm for the excitation energy of 365 nm due to the n-π* and π-π* transitions of the azobenzene chromophore. Thermal properties were also studied using TGA analysis. Stimuli-responsive polymers are widely used in optoelectronics and photonics, such as optical switching, optical information storage devices, liquid crystal display technology, and diffractive optical elements. [ABSTRACT FROM AUTHOR]

Over the last three decades, there has been considerable interest in the captivating mechanical properties displayed by auxetic materials, highlighting the advantages stemming from their distinct negative Poisson's ratio. The negative Poisson's ratio observed in auxetic polymeric materials is a result of the distinctive geometries of their unit cells. These unit cells, encompassing structures such as chiral, re-entrant, and rotating rigid configurations, are carefully engineered to collectively generate the desired auxetic behaviour. This comprehensive review article explores the field of auxetic polymeric materials, offering a detailed exploration of their geometries, fabrication methods, mechanical properties, and characterisation. The diverse applications of these materials in impact/ballistic, acoustic, automotive, biomedical, sports, shape memory, strain sensors, electromagnetic shielding, smart filters, and rehabilitation fields are thoroughly examined. Furthermore, the article emphasises the significance of auxetic behaviour in enhancing mechanical performance while shedding light on the challenges and limitations associated with large-scale fabrication of auxetic materials. [ABSTRACT FROM AUTHOR]

In this paper, we report the microstructural investigation and influence of H-bonding on the thermal behavior e.g., glass transition (Tg) and thermal degradation of chiral copolymers of (R)- N-(1-phenyl-ethyl) methacrylamide (R-NPEMAM) and 2-hydroxy ethyl methacrylate (HEMA). The Tg increases with the increase of chiral unit content in the copolymers and then attains optimum at around 25 mole % of chiral content. Thereafter it decreases with the increase of chiral content. The effect of copolymer composition and secondary interaction associated with the Hbonding on the thermal properties of these copolymers was also studied. Secondary interaction, specifically H-bonding has been interpreted using FTIR analysis. The copolymers thermally degrade in three stages. The first and third stages of degradation are associated with the chiral comonomer (R-NPEMAM) whereas the second stage indicates the degradation due to HEMA unit present in the copolymer chain. The activation energies for these degradations of the copolymers have been evaluated using Flynn-Wall and Kissinger method. [ABSTRACT FROM AUTHOR]

We report the synthesis and characterization of multifunctional polysilane copolymers containing chiral and azobenzene chromophore as a pendant group. Multifunctional polymers of poly(methylphenylsilane) (PMPS) with (R)-N-(1-phenylethyl)methacrylamide (R-NPEMAM) and disperse red 1 methacrylate (DR1MA) were synthesized in a quartz tube using UV-technique. The molecular weights of such synthesized copolymers were found to be in the order of 103. The appearance of two glass transition temperatures in DSC indicated that the synthesized copolymers are block copolymers. The electronic absorbance of synthesized polymers was observed at 272 nm (π-π* transition of aromatic ring), 330 nm (σ-σ* transition of Si-Si chain of PMPS) and 475 nm (n-π* with π-π* transition due to azobenzene chromophore of DR1MA unit). The chirality of the synthesized polymer was confirmed through circular dichroism observed at 261 nm. Induced chirality appeared at 330 nm and 470 nm due to the association of the Si-Si chain of PMPS and the presence of azobenzene chromophore of the DR1MA unit respectively. The photoluminescence (PL) properties of the synthesized copolymers (SCDRDM-1B, SCDRDM-2B, and SCDRDM-3B) were observed at 307 nm and 415 nm when excited at 275 nm. The λem was also observed at 415 nm when excited by 325 nm. The multi-emission spectra appeared at 500 nm, 550 and 590 nm are presumed to be due to exciton coupling between azobenzene chromophore of DR1MA, and Si-Si σ-conjugation in association with the aromatic ring of PMPS and chiral unit R-NPEMAM block. [ABSTRACT FROM AUTHOR]

Functional photoactive polysilane copolymers of poly(methylphenylsilane) (PMPS) and disperse yellow 7 methacrylate (DY7MA) were synthesized using UV-technique. In the same manner functional polysilane copolymers of poly(methylphenylsilane-co-dimethylsilane) (CPS) and disperse yellow 7 methacrylate (DY7MA) were also synthesized. By the UV irradiation polysilanes (PMPS and CPS) give rise to silyl macroradicals which initiate the polymerization of photoactive monomer (DY7MA). The synthesized samples were characterized by FTIR, NMR, and UV-Vis spectroscopy. The molar mass of synthesized photoactive functional polysilane copolymers is of order of 103gm/mol. They exhibited multimodal optical and photoluminescence functional properties. Optical absorbance was observed at 336 nm due to σ-σ* transition of σ-conjugation of Si-Si main chain. The other absorbance at 276 nm is due to π-π* transition of aromatic ring associated with polysilanes and DY7MA polymeric unit. The electronic absorption was observed at 367 nm for π-π* and n-π* transition of azobenzene chromophores of DY7MA. The photoemission spectra are observed at λem = 405, 428 and 454 nm for the excitation energy of 332 and 370 nm. Such functional polysilane copolymers exhibited two glass transition temperatures indicating the formation of block copolymers. The synthesized functional polysilane copolymers are thermally stable upto 300ºC. Such functional photoactive block copolymers may find novel optoelectronic applications. [ABSTRACT FROM AUTHOR]

The multifunctional double network (DN) soft hydrogels reported here are highly swellable and stretchable pH‐responsive smart hydrogel materials with sufficient strength and self‐healing properties. Such multifunctional hydrogels are achieved using double crosslinking structures with multiple physical and chemical crosslinks. They consist of a copolymer network of acrylamide (AM) and sodium acrylate (Na‐AA) and other reversible network of poly(vinyl alcohol)–borax complex. They were characterized by Fourier transform IR analysis and studied for their hydrogen bonding and ionic interaction. The degree of equilibrium swelling was observed to be as high as 5959% (at pH 7.0) for a hydrogel with AM/Na‐AA = 25/75 wt% in the network (GS‐6 sample). The highest degree of swelling was observed to be 6494% at pH 8.5. The maximum tensile strength was measured to be 1670, 580 and 130 kPa for a DN hydrogel (GS‐2 sample: AM/Na‐AA =75/25 wt% with 20, 40 and 60 wt% water content, respectively). The self‐healing efficiency was estimated to be 69% for such a hydrogel. These multifunctional DN hydrogels with amalgamation of many functional properties are unique in hydrogel materials and such materials may find applications in sensors, actuators, smart windows and biomedical applications. © 2018 Society of Chemical Industry Multifunctional double network pH‐responsive smart hydrogels have been developed which are highly swellable and stretchable with sufficient strength and self‐healing properties. Such hydrogels are based on double crosslinking structures with multiple physical and chemical crosslinks of a network of acrylamide and sodium acrylate embedded into another reversible network of poly(vinyl alcohol)–borax complex. [ABSTRACT FROM AUTHOR]

Crosslinking is one of the most important factors affecting the major characteristics of polymer and hydrogel materials. Now-a-days, double network (DN) hydrogels have attracted special attention for their high strength and stretchability. In this investigation, we report the effect of crosslinker concentration on the DN hydrogels which are consisting of poly(vinyl alchohol)-borax as the first network and poly(acrylamide-co-2-hydroxyethyl methacrylate) as the second network synthesized by in-situ crosslinking polymerization process using N, N'-methylenebisacrylamide (MBA) as crosslinker. Various properties of the DN hydrogels such as degree of swelling, swelling kinetics, gel fraction and network parameters (crosslink density, average molar mass between crosslinks, mesh size etc.) were studied. The polymer-solvent interaction parameter (χ) and polymer volume fraction in swollen state (VP) were also calculated using Flory-Rehner Theory. We observed that the degree of swelling was increased with increasing crosslinker concentration up to 0.1 wt% of monomers. But above this concentration, it was decreased with crosslinker concentration. The gel fractions as well as mechanical properties were increased with increasing MBA crosslinker concentration. [ABSTRACT FROM AUTHOR]

(R)-N-(1-phenyl-ethyl) methacrylamide (R-NPEMAM) was synthesized which is an organic chiral monomer. The crystals of such monomer were obtained by recrystallization of the synthesized product from ethanol-water mixture. It was polymerized with 2-hydroxyethyl methacrylate (HEMA) and a crosslinking monomer, N,N ' methylene bisacrylamide in toluene medium. These materials have been characterized by different analytical techniques such as FTIR, elemental and SEM analyses for their structural and morphological investigation. The organic monomer is a chiral molecule and its optical rotation was observed to be: [α]D25=28° (C 1.0 DMF). On the other hand, optical rotations were observed to be: 35° for its polymer (CP) and 8 to 21° for its copolymers having different chiral content. Such organic and polymeric materials were studied for their NLO properties. The relative second harmonic generation (SHG) efficiency of organic chiral monomer crystal (CCM) was 1.22 times that of KDP, whereas the values of polymer and copolymers were slightly less (0.87 to 0.94) than that of the KDP crystal. However, all these values are comparable to the property of other organic crystals and also to the recently reported SHG efficiency of 1.5 times for organic 4-chloroanilinium-L-tartrate monohydrate single crystal. These materials may find their potential nonlinear optical applications. [ABSTRACT FROM AUTHOR]

Nanocomposites were prepared using copper nanoparticles as filler material and epoxy as matrix by casting process. The effect of copper nanoparticles on mechanical and wear properties of the nanocomposites were investigated in details. Copper nanofillers contributed significantly to improve the anti-wear property of the nanocomposites. The specific wear rate of epoxy was reduced by 80% due to incorporation of 1.5 wt% of filler into the matrix resin. However, it marginally increased for further incorporation of copper nanoparticles from 1.5 wt% up to 2.5 wt%. This reduction of wear rate in first case is obvious due to uniform dispersion of copper nanoparticles in the matrix, whereas increase of wear rate in the second case may be the agglomeration of nanoparticles in the matrix at higher filler loading. The maximum flexural strength of 117.78 MPa and flexural modulus of 3.67 GPa were achieved in nanocomposites having 1.5 wt% copper nanoparticles, whereas such values are 106.89 MPa and 2.59 GPa respectively for neat epoxy (without nanoparticles). The wear and mechanical properties of nanocomposites were correlated with SEM analysis of worn surfaces and fractured surfaces. Thermal properties of nanocomposites were also evaluated by Thermogravimetric Analysis (TGA). [ABSTRACT FROM AUTHOR]

In this investigation, we report double network (DN) hydrogels having high mechanical strength at their swollen state. Such a double network hydrogel is consisting of PVA-borax double strand in which P(AM-HEMA) crosslinked network was embedded by in-situ polymerization. Both the swelling property and tensile strength of the hydrogels (in their swollen state) depends on the composition of the hyrogels. The equilibrium swelling ratio was achieved as high as 1272% for a sample where AM/HEMA=100/0 was taken in the second network (no HEMA). The compositional ratio of AM and HEMA in forming double network has also distinct influence on the mechanical properties of the hydrogels. The tensile strength values for DN hydrogels having 80 wt% water content were measured to be 21.77kPa, 31.47 kPa and 32.21 kPa for the DN hydrogels having AM/ HEMA weight ratio 67/33, 50/50 and 25/75 (PVA-borax content being constant). Elongation of more than 200% was also achieved in such a DN hydrogel. The results obtained in this system of DN hydrogels having PVA-borax network are comparable with those reported for other systems. The high mechanical properties of such hydrogels can be attributed to the reinforcing influence of PVA-borax complex crosslinking onto the P(AM-HEMA) networks. [ABSTRACT FROM AUTHOR]