Dibyendu S. Bag

Chemical modification of LDPE film

Low-density polyethylene (LDPE) film was chemically modified by chromic acid treatment to generate polar groups on the surface. The film samples were etched by chromic acid with variation of temperature at a constant time (30 min) and variation of time at a constant temperature (room temperature = 26°C). The variation of weight and thickness of the film samples before and after etching was measured. The surface morphology of the etched films was studied by Scanning Electron Microscopy (SEM). IR and XPS analysis revealed the introduction of polar groups like COOH, 〉CO, SO3H on the etched LDPE film surface, which exhibited improved printability. Etching also enhanced adhesion with epoxy resin. The mechanical properties of the laminates of the two specimens of the same film sample with epoxy resin were also measured.

Surface modification and evaluation of polyethylene film

Abstract LDPE and a blend of LDPE and LLDPE (50/50) films were etched by hot fuming nitric acid to introduce polar groups on the film surfaces. The presence of polar groups, mainly, COOH, >CO, NO 2 and NO, was confirmed by IR studies. Deconvolution of the ESCA peaks also supported the generation of active polar groups. The surface morphology of the etched films was studied by scanning electron microscopy. The mechanical performance of laminates of these active films with epoxy (Araldite) resin was tested by tensile property measurement.

Polymerization under magnetic field—II. Radical polymerization of acrylonitrile, styrene and methyl methacrylate

Radical polymerization of acrylonitrile (AN), methyl methacrylate (MMA) and styrene (S) has been studied under magnetic field (MF) using an AIBN initiator. The effect of MF is observed on the polymerization of AN and not on MMA and styrene. This may be due to the heterogeneous polymerization of AN (occlusion theory). The MF increases the rate of AN polymerization and polymer (PAN) yield. The overall activation energy is not influenced by the MF; however, the MF helps to reduce the activation entropy of polymerization. The influence of MF alters the structure and properties of the polyacrylonitrile (PAN). The molecular weight (MW) of PAN prepared under MF is higher and the molecular weight distribution (MWD) is narrower than those obtained without MF. The syndiotactic stereoregularity and crystallinity of such PAN polymer is higher than that obtained without application of MF. Magnetic field enhances the thermostability and the dielectric property of PAN.

Polymerization under a magnetic field. VI. Triplet dye‐sensitized photopolymerization of acrylamide and methyl methacrylate

Methylene blue sensitized photopolymerization of acrylamide (AM) and methyl methacrylate (MMA) using triethanolamine or the sodium salt of EDTA as a reducing agent has been investigated under the influence of a magnetic field (0-7.3 kG). There was no effect of the magnetic field (MF) on the polymerization of AM and MMA in aqueous medium. However, in the water-methanol mixture (1: 1) the yield of polymer decreases and the molecular weight increases in both cases under MF. This has been explained on the basis of the triplet mechanism.

X‐ray photoelectron spectroscopy: A new method for determination of copolymer composition, and monomer reactivity ratios and monomer sequence distribution therefrom

Copolymer compositions and reactivity ratios for the radical copolymerization of styrene with acrylonitrile have been determined by x-ray photoelectron spectroscopy (XPS). The results obtained by this technique were confirmed by elemental as well as 1H-NMR (nuclear magnetic resonance) analysis. The monomer sequence distributions have also been calculated utilizing the monomer reactivity ratio values obtained by three different techniques viz., XPS, 1H-NMR, and elemental analysis. The agreement between the monomer sequence distributions in the copolymer chain by these methods is very satisfactory.

Synthesis and characterization of functional photoactive organic-inorganic block copolymers of poly(methylphenylsilane) and disperse red 1 methacrylate and study of their optical and photophysical properties

ABSTRACT Functional photoactive organic-inorganic block copolymers of poly(methylphenylsilane) (PMPS) and disperse red 1 methacrylate (DR1MA) were synthesized in a quartz tube using UV-technique. The synthesized block copolymers were characterized by FTIR, NMR, GPC and thermal analyses and studied for their optical and photoluminescence properties. The weight average and number average molecular weights of such a synthesized block copolymer are 2.47 × 103 and 2.27 × 103, respectively. The appearance of two glass transition temperatures indicated the synthesized polymers as block copolymers. The functional organic-inorganic block copolymers exhibited optical absorbance at 276 nm due to aromatic ring associated with both the blocks and at 325 nm due to σ-electron delocalization of Si-Si chain of PMPS block. Also, the optical absorbance appeared at 472 nm is due to combining the contribution of n-π* and first π-π* charge transfer electronic transition of the azobenzene chromophore of DR1MA unit. Two photoemissions were observed at 307 nm and 415 nm when such a polymer was excited at 275 nm. The photoluminescence was also observed at 415 nm when excited by 325 nm. The multi-emission spectra appeared between 510 nm to 580 nm are presumed to be due to exciton coupling between azobenzene chromophore of DR1MA and and Si-Si σ-conjugation of PMPS block. The synthesized copolymers are thermally stable up to 260°C. Such functional photoactive block copolymers may find novel optoelectronic application.

Polymerization under Magnetic Field. Part 9. Polymerization of 2-Hydroxyethyl Methacrylate by Benzoyl Peroxide

A systematic investigation of the influence of Magnetic Field on polymerization and copolymerization has been carried out on 2-hydroxyethyl methacrylate under UV-irradiation using benzoyl peroxide as initiator.