Plasmochemical modification of polymer surfaces

Influence of low-temperature plasma on the polymer surface was studied with the aim of preparing polymers with required surface properties.     

Electrochemical modification of polypyrrole films for imparting hemocompatible properties to hemosorbent

A method of production of hemosorbent based on thermally expanded graphite is developed. The method involves the electropolymerization of pyrrole on rolled thermally expanded graphite and subsequent cyclic electrochemical doping of polypyrrole film with Cl^? anions. The method enables one to produce a hemosorbent with an open-circuit potential, which is necessary for its biocompatibility.     

Synthesis of hemocompatible materials based on branched polyvinyl alcohol

The possibility of modification of polyvinyl alcohol with epichlorohydrin was examined with the aim of preparing hemocompatible materials exhibiting high mechanical density at limited swellability. The conditions of modification and preparation of branched polyvinyl alcohol and of hemocompatible hydrogel systems with improved operation properties were determined.     

Synthesis of novel fluorocarbon ether bibenzoxazole polymers

Novel fluorocarbon bis(o-aminophenol) monomers were synthesized by a multistep route from 1,3-diiodohexafluoropropane and 1,8-diiodohexadecafluorooctane. The acetic acid-promoted polycondensation of these monomers with fluorocarbon ether-diimidate esters led to linear, soluble fluorocarbon ether-bibenzoxazole polymers with inherent viscosities in the range of 0.10–0.94 dl/g^?1. Polymer structures were verified by elemental and infrared (IR) spectral analysis. Many of the polymers exhibited considerable crystallinity in which the crystalline melt temperatures ranged from 53 to 187°C, as determined by differential scanning calorimetry. Some polymers, however, were isolated as completely amorphous, rubbery gums that exhibited glass transition temperatures as low as ?31°C. Good thermooxidative stabilities were exhibited with onset of weight loss of the polymers during thermogravimetric analysis in an air atmosphere occurring in the 375–450°C range.     

FI catalysts: new olefin polymerization catalysts for the creation of value-added polymers

This contribution reports the discovery and application of phenoxy-imine-based catalysts for olefin polymerization. Ligand-oriented catalyst design research has led to the discovery of remarkably active ethylene polymerization catalysts (FI Catalysts), which are based on electronically flexible phenoxy-imine chelate ligands combined with early transition metals. Upon activation with appropriate cocatalysts, FI Catalysts can exhibit unique polymerization catalysis (e.g., precise control of product molecular weights, highly isospecific and syndiospecific propylene polymerization, regio-irregular polymerization of higher alpha-olefins, highly controlled living polymerization of both ethylene and propylene at elevated temperatures, and precise control over polymer morphology) and thus provide extraordinary opportunities for the syntheses of value-added polymers with distinctive architectural characteristics. Many of the polymers that are available via the use of FI Catalysts were previously inaccessible through other means of polymerization. For example, FI Catalysts can form vinyl-terminated low molecular weight polyethylenes, ultra-high molecular weight amorphous ethylene-propylene copolymers and atactic polypropylenes, highly isotactic and syndiotactic polypropylenes with exceptionally high peak melting temperatures, well-defined and controlled multimodal polyethylenes, and high molecular weight regio-irregular poly(higher alpha-olefin)s. In addition, FI Catalysts combined with MgCl(2)-based compounds can produce polymers that exhibit desirable morphological features (e.g., very high bulk density polyethylenes and highly controlled particle-size polyethylenes) that are difficult to obtain with conventionally supported catalysts. In addition, FI Catalysts are capable of creating a large variety of living-polymerization-based polymers, including terminally functionalized polymers and block copolymers from ethylene, propylene, and higher alpha-olefins. Furthermore, some of the FI Catalysts can furnish living-polymerization-based polymers catalytically by combination with appropriate chain transfer agents. Therefore, the development of FI Catalysts has enabled some crucial advances in the fields of polymerization catalysis and polymer syntheses.     

Ionic polymers as a new structural motif for high-energy-density materials

Energetic materials have been used for nearly two centuries in military affairs and to cut labor costs and expedite laborious processes in mining, tunneling, construction, demolition, and agriculture, making a tremendous contribution to the world economy. Yet there has been little advancement in the development of altogether new energetic motifs despite long-standing research efforts to develop superior materials. We report the discovery of new energetic compounds of exceptionally high energy content and novel polymeric structure which avoid the use of lead and mercury salts common in conventional primary explosives. Laboratory tests indicate the remarkable performance of these Ni- and Co-based energetic materials, while DFT calculations indicate that these are possibly the most powerful metal-based energetic materials known to date, with heats of detonation comparable with those of the most powerful organic-based high explosives currently in use.     

Synthesis and copolymerization of new methacrylic monomers for the creation of nonlinear optical polymer materials

A new methacrylic monomer, 3,5-bis[2-(N-ethylanilino)ethoxy]benzyl methacrylate (MBA), has been synthesized. Methacrylic copolymers with different content of bi-chromophore fragments in the side chain were obtained by radical copolymerization of methyl methacrylate and MBA, followed by azo-functionalization reaction. The composition of the obtained copolymers was established, and their thermal properties were determined. Thin films of synthesized copolymers were prepared by spin-coating and the nonlinear optical characteristics of the obtained materials were investigated.

     

Polymerization of supramonomers: A new way for fabricating supramolecular polymers and materials

Supramolecular polymers and materials are attracting more and more attention nowadays due to their dynamic properties such as reversibility, stimuli-responsiveness and self-healing. Conventionally, bifunctional or multi-functional monomers are first covalently synthesized, followed by the supramolecular complexation to form supramolecular polymers and materials. Recently, we have proposed the supramonomer concept to construct supramolecular polymers and materials in a different way. Supramonomers are bifunctional or multi-functional monomers fabricated by noncovalent synthesis, but can undergo traditional covalent polymerization. In this highlight article, we will summarize and discuss the fabrication of supramonomer and covalent polymerization methods of supramonomers; fabrication of multi-responsive supramolecular polymers from supramonomers; and fabrication of supramolecular materials from supramonomers. It is highly anticipated that the supramonomer concept will enrich the methodology towards supramolecular polymers and materials. © 2016 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2017 , 55, 604–609     

Surface modification of biomedical polymers

Surface modification of biomedical polymers by the technique of surface grafting was briefly overviewed, mostly based on our results. It was shown that surface grafting of water-soluble polymer chains onto polymeric biomaterials was effective in producing mechanically non-stimulative, blood-compatible, antibacterial, tissue-bonding, and cell-adhesive surfaces. In addition to the improvement of the interfacial biocompatibility, the surface grafting was useful also for obtaining a biofunctional surface such as immunoadsorbent.     

Graft copolymerization of 2‐methacryloyloxyethyl phosphorylcholine to cellulose in homogeneous media using atom transfer radical polymerization for providing new hemocompatible coating materials

To develop new hemopurification systems based on cellulose membrane, we synthesized a graft copolymer of cellulose with poly(2‐methacryloyloxyethyl phosphorylcholine) (MPC) by a metal‐catalyzed atom transfer radical polymerization process in homogeneous media. First, cellulose was dissolved in a DMAc/LiCl solution system, and it reacted with 2‐bromoisobutyloyl bromide to produce macroinitiator (cell‐BiB). Then, MPC was polymerized to the cellulose backbone in a homogeneous DMSO/methanol mixture solution in the presence of cell‐BiB. Characterization with FT‐IR, NMR, and GPC measurements showed that there obtained a graft copolymer of cellulose backbone and poly(MPC) side chains (cell‐PMPC) with well‐defined structure, indicating a controlled/“living” radical polymerization. The proteins adsorption studies showed that cellulose membranes modified by the as‐prepared cell‐PMPC owns good protein adsorption resistance. © 2008 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 46: 3306–3313, 2008     

Radiation modification of semicrystalline polymers

Three problems of the radiation modification of polymers are dealt with. Different methods of grafting are compared with respect of the formation of true graft copolymer and homopolymer in the polyethylene-styrene system; the prevention of the penetration of monomer by grafting polytetrafluoroethylene is shown; the mechanical properties of crosslinked ethylene polymers below and above the melting point are discussed.     

Simultaneous thermogravimetry-mass spectrometry and pyrolysis—gas chromatography of fluorocarbon polymers

The thermal degradation of polytetrafluoroethylene (PTFE) and tetrafluoroethylene/hexafluoropropylene copolymer (FEP) has been investigated in different gas atmospheres by simultaneous thermogravimetry—mass spectrometry, pyrolysis—gas chromatography, combined gas chromatography—mass spectrometry, and IR analysis.There are no significant differences in the decomposition products of the two polymers in helium or air at a temperature range of 450–790°C; C₁ to C₈ fluorocarbons and their oxidized products have been identified. The various fluorocarbons produced are plotted against the degradation temperature, and at temperatures of 450–550°C FEP evolves large amounts of tetrafluoroethylene formed by a decomposition reaction of perfluoropropylene.From the traces of the TG-MS in an atmosphere of helium, the FEP clearly decomposes in two stages. The first stage degradation is mostly attributed to the evolution of perfluoropropylene with a small amount of perfluoro-1-butene or perfluoroisobutylene, and possibly traces of perfluorocyclobutane. Tetrafluoroethylene is evolved with these fluorocarbons at the second stage degradation, showing similar characteristics of the degradation mechanisms of FEP at the two stages. In the presence of air, the two polymers also decompose in two stages. Activation energies for the degradation products are calculated, and the decomposition mechanisms of the polymers are discussed with the results of IR analysis.     

Chromatography of functional polymers: A new approach to the characterization of reactive polymers obtained by chemical modification

High-performance liquid chromatography (HPLC) has been used to complement size-exclusion (gel permeation) chromatography (SEC) for the characterization of functional polymers. Whereas SEC is unable to detect compositional changes, HPLC in an appropriate interacting medium can provide detailed information on compositional changes occurring during chemical modification of a polymer. The method has been demonstrated using a normal-phase column consisting of porous monodisperse 10 μm poly(2,3-dihydroxypropyl methacrylate-co-ethylene dimethacrylate) beads that have a homogeneous coverage of aliphatic hydroxyl groups for the analysis of brominated poly(isobutylene-co-4-methylstyrene). Differences of well below 1 mol % of bromomethylstyrene units are easily detected and quantified. © 1997 John Wiley & Sons, Inc. J Polym Sci A: Polym Chem 35: 1173–1180, 1997     

Preparation of bio-based polymers for materials applications

A new technology developed by us for the synthesis of well defined, tailored cellulose-synthetic polymer graft polymers and crosslinked cellulose graft polymers with control over the molecular weight of the synthetic polymer graft, a high degree of graft substitution, and knowledge of the backbone-graft linkage is reviewed. The potential of bio-based polymers using these new tailored cellulosic graft polymers for use in plastics, resins, and composite applications is discussed. The new graft polymers can function as compatibilizers/interfacial agents in the preparation of biopolymer-synthetic polymer composites and blends with the desirable properties of the constitutent polymers incorporated into the new material system.     

Synthesis and physical–chemical properties of hydrolyzed nanosized mesoporous fluorocarbon materials and carbon–fluorocarbon composites

Hydrolysis of nanosized mesoporous superstoichiometric fluorocarbon material FS (CF_{1.20 ± 0.03}) and carbon–fluorocarbon nanocomposites NCFC (CF_{0.93 ± 0.03}) by 10% KOH in aqueous-alcohol solution was studied and yielded two new classes of the hydrolyzed fluorocarbon nanomaterials: hydroxofluorocarbon nano-material FS–OH of general formula sp³-C_1−yF_n−x(OH)_x (n = 1; x > 0.1, y ∼ 0.05–0.1) and carbon–hydroxofluorocarbon nanocomposites NCFC–OH of general formula sp²-C_m*sp³-C_1−yF_n−x(OH)_x (n = 1; x ∼ 0; y ∼ 0.1–0.2).FTIR and Raman studies of FS–OH and NCFC–OH materials have shown that hydrolysis of sp³-C–F-bonds in these materials leads a decrease of sp³-C–F amount and appearance of characteristic absorption bands for sp³-C–OHO, carboxyls and carbonyls, typical for oxidized graphites, carbon blacks and various soots. These phenomena, in combination with C,H,F-analyses for FS–OH and NCFC–OH products have allowed to state that hydrolysis of FS and NCFC in KOH solutions can be explained by the substitution reactions of surface sp³-C–F to sp³-C–OH and sp²>CO containing groups.Observed hydrolytic reactions are also accompanied with processes of the colored solutions origin (yellow – for FS and red-brown – for NCFC). These solutions have UV-VIS spectra identical to graphene oxide and graphitic acid.     

Accessible new acrylic monomers and polymers as highly transparent organic materials

Theoretical studies of intrinsic absorption phenomena in organic compounds in a range of wavelengths from visible to near-infrared (NIR), led us to synthesize acrylic monomers with variable molar number of CH per cubic centimeter, N_CH. Thus, halogenoalkyl or aryl α-chloroacrylates, α-fluoroacrylates, and methacrylates are prepared. The corresponding homo- and copolymers exhibit good thermal (T_g from 120 to 160°C) and optical properties.