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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]

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]

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]