Search results for " Plastics"
showing 10 items of 2628 documents
Soluble Hyperbranched Poly(glycolide) Copolymers
2010
A series of (hyper)branched poly(glycolide) copolymers has been prepared by copolymerization of glycolide (GA) with 2,2-bis(hydroxymethyl)butyric acid (BHB) via combined ROP/AB2-polycondensation. Polymerization was conducted in bulk and catalyzed by stanneous-2-ethyl hexanoate (Sn(Oct)2). The branched topology of the resulting polyesters was studied in detail by 1D- and 2D-NMR spectroscopy and confirmed by the synthesis and characterization of model compounds. The AB2 monomer BHB was incorporated either as a dendritic or focal unit, but hardly in linear or terminal mode. As expected for multifunctional polycondensation, SEC measurements showed polydisperse products with polydispersity index…
Molecular parameters of hyperbranched polymers made by self-condensing vinyl polymerization. 1. Molecular weight distribution
1997
The molecular weight distribution (MWD) and its moments are calculated for hyperbranched polymers formed by self-condensing vinyl polymerization (SCVP) of monomers (“inimers”) with the general structure AB*, where A is a vinyl group and B* is an initiating group. The calculated MWD is extremely broad, the polydispersity index (PDI) being equal to the number-average degree of polymerization: Pw/Pn = Pn. It is twice as broad as that for the polycondensation of AB2 type monomers. If the fraction of unreacted monomer is not taken into account, the MWD becomes somewhat narrower, P‘w/P‘n ≈ 0.40P‘n. The kinetics of the polymerization process are first order with respect to the concentration of vi…
Hyperbranched Polylactide Copolymers
2006
A series of hyperbranched poly(l-lactide) (PLLA) copolymers were prepared by copolymerization of dilactide with 2,2-bis(hydroxymethyl)butyric acid (BHB) as an AB2 comonomer via a combined ring-open...
Linear Organo-Soluble Poly(p-benzamide)
2009
Organo-soluble, shape-persistent oligo- and poly(p-benzamide)s were synthesized and characterized. A triethylene glycol (TEG) substituent was introduced to the p-aminobenzoic acid monomer structure as a solubilizing side chain giving 4-amino-2-triethylene glycol benzoic acid. This new monomer was polymerized by the facile polycondensation of the corresponding acid halide derivative of the amine hydrochloric salt. Additionally, a well-defined heptamer was prepared from this monomer on a peptide synthesizer as a model compound. The TEG-substituted oligomers and polymers exhibited good solubility yet high aggregation tendency in common polar and nonpolar organic solvents. The solution self-org…
Water-soluble polyesters from long chain alkylesters of citric acid and poly(ethylene glycol)
2007
Abstract Long chain aliphatic alcohols have been used as model compounds to develop a preparative method for a water-soluble material, which could be a carrier for triacontanol, a highly hydrophobic plant growth regulator. New polyesters from long chain aliphatic (C = 12, 18 and 22) mono-1-alkyl citrates and poly(ethylene glycol) were synthesized and characterized by NMR spectroscopy. The polyester containing the triacontyl moiety was obtained from mono-1-triacontyl citrate, which was synthesized from the corresponding alcohol extracted from the Agave fourcroydes . The molecular weight M ¯ n of the polyesters depends on experimental conditions during synthesis such as reaction time, atmosph…
Properties of trialkylamines as catalysts of resoles synthesis
2000
A series of the syntheses of phenol–formaldehyde resoles was carried out in the presence of trimethyl-, triethyl-, tripropyl-, and tributylamines and sodium hydroxide as catalysts for this process. The rate constants were calculated for the partial reactions identified in the synthesis. Also, the performance properties of the resins obtained and the hardened resin samples were estimated in simple tests. © 2000 John Wiley & Sons, Inc. J Appl Polym Sci 77: 898–902, 2000
Fluctuating Interfaces in Liquid Crystals
2008
We review and compare recent work on the properties of fluctuating interfaces between nematic and isotropic liquid-crystalline phases. Molecular dynamics and Monte Carlo simulations have been carried out for systems of ellipsoids and hard rods with aspect ratio 15:1, and the fluctuation spectrum of interface positions (the capillary wave spectrum) has been analyzed. In addition, the capillary wave spectrum has been calculated analytically within the Landau-de Gennes theory. The theory predicts that the interfacial fluctuations can be described in terms of a wave vector dependent interfacial tension, which is anisotropic at small wavelengths (stiff director regime) and becomes isotropic at l…
Shear Modulus of an Irreversible Diblock Copolymer Network from Self-Consistent Field Theory
2019
Using self-consistent field theory, we investigate the stretching-induced microphase separation in an irreversibly cross-linked polymer network composed of diblock copolymer chains and estimate its...
Electrically conductive hydrogel composites made of polyaniline nanoparticles and poly(N-vinyl-2-pyrrolidone)
2006
Abstract A novel electrically conductive composite material, consisting of polyaniline (PANI) nanoparticles dispersed in a polyvinyl pyrrolidone (PVP) hydrogel, was prepared ‘in situ’ by water dispersion polymerisation (DP) of aniline using PVP as steric stabiliser, followed by γ-irradiation induced crosslinking of the PVP component. Conversion yield of aniline into PANI particles was determined via HPLC and gas chromatography, while structural confirmation of the synthesised polymer was sought by FTIR. Morphology and dimensions of PANI particles into the coloured, optically transparent hydrogel was determined by electronic microscopy; moreover, swelling behaviour of composite hydrogels in …