Incorporation of biguanide compounds into poly(GL)-b-poly(GL-co-TMC-co-CL)-b-poly(GL) monofilament surgical sutures

A new biodegradable coating was developed for bioabsorbable monofilament sutures. Specifically, a random copolymer having 35 wt-% and 65 wt-% of lactide and trimethylene carbonate units showed appropriate flexibility, stickiness and degradation rate, as well as capability to produce a complete and uniform coating. Monofilament sutures of polyglycolide-b-poly(glycolide-co-trimethylene carbonate-co-e-caprolactone)-b-polyglycolide were loaded with chlorhexidine (CHX) and poly(hexamethylene biguanide) (PHMB) to explore the possibility to achieve antimicrobial activity without adverse cytotoxic effects. To this end, two processes based on single drug adsorption onto the suture surface and incorporation into the coating copolymer were used and subsequently evaluated. Although the second process could be considered more complex, clear benefits were observed in terms of drug loading efficiency, antimicrobial effect and even lack of cytotoxicity. In general, drugs could be loaded in an amount leading to a clear bacteriostatic effect for both Gram-negative and Gram-positive bacteria without causing significant cytotoxicity. Release profiles of PHMB and CHX were clearly different. Specifically, adsorption of the drug onto the fiber surface which prevented complete release was detected for PHMB. This polymer had advantages derived from its high molecular size, which hindered penetration into cells, thus resulting in lower cytotoxicity. Furthermore, bacterial growth kinetics measurements and bacterial adhesion assays showed greater effectiveness of this polymer.Peer ReviewedPostprint (author's final draft

Polyvinyl Acetate Lattices as Adhesives for Pigment-Coated Paper

In recent years, the possibility of using synthetic latices as adhesives in the paper coating industry has caused much interest. The manufacturers of latices uncovered a new market by fostering developmental research in the field of pigment coating binders. Polyvinyl acetate latices were one of the group of products studied in this manner. In the past, experts in the field of coating believed that synthetic latices could contribute substantial improvements to some optical properties of coated papers over and above that of conventional adhesives. It was also felt that synthetic latices could exhibit higher pigment binding power than conventional adhesives. Recently, Hsia (1) found that polyvinyl acetate latex produced significant improvements of optical properties of coated papers over and above those of conventional casein based coatings. However, the pigment binding power of casein was found to higher than that of the polyvinyl acetate latex used by Hsia. The purpose of this study was to explore further, the significant results of Hsia\u27s investigation

Heparin-containing block copolymers, Part I: Surface characterization

Newly synthesized heparin-containing block copolymers, consisting of a hydrophobic block of polystyrene (PS), a hydrophilic spacer-block of poly(ethylene oxide) (PEO) and covalently bound heparin (Hep) as bioactive block, were coated on aluminium, glass, polydimethylsiloxane (PDMS), PS or Biomer substrates. Surfaces of coated materials were characterized by transmission electron microscopy (TEM), contact angle measurements and X-ray photoelectron spectroscopy for chemical analysis (XPS). It was demonstrated by TEM that thin films of PS-PEO and PS-PEO-Hep block copolymers consisted of heterogeneous microphase separated structures. Using sessile-drop and Wilhelmy plate dynamic contact angle measurements, insight was provided into the hydrophilicity of the surfaces of the coatings. Measurements with hydrated coatings of PS-PEO and PS-PEO-Hep block copolymers revealed that the surfaces became more hydrophilic during immersion in water, due to relaxation/reorientation, or swelling of PEO or PEO-Hep domains, respectively. XPS results for PS, PEO, heparin and PS-PEO as powder agreed well with qualitative and quantitative predictions. XPS results for films of PS-PEO and PS-PEO-Hep block copolymers showed enrichments of PEO in the top layers of the coatings. This effect was more pronounced for hydrated surfaces. Only small amounts of heparin were detected at the surface of coatings of PS-PEO-Hep block copolymers

Inorganic-organic separators for alkaline batteries

A flexible separator is reported for use between the electrodes of Ni-Cd and Ni-Zn batteries using alkaline electrolytes. The separator was made by coating a porous substrate with a battery separator composition. The coating material included a rubber-based resin copolymer, a plasticizer and inorganic and organic fillers which comprised 55% by volume or less of the coating as finally dried. One or more of the filler materials, whether organic or inorganic, is preferably active with the alkaline electrolyte to produce pores in the separator coating. The plasticizer was an organic material which is hydrolyzed by the alkaline electrolyte to improve conductivity of the separator coating

Enhancing ordering dynamics in solvent-annealed block-copolymer films by lithographic hard masks supports

We studied solvent-driven ordering dynamics of block copolymer films supported by a densely cross-linked polymer network designed as organic hard mask (HM) for lithographic fabrications. The ordering of microphase separated domains at low degrees of swelling corresponding to intermediate/strong segregation regimes was found to proceed significantly faster in films on a HM layer as compared to similar block copolymer films on silicon wafers. The ten-fold enhancement of the chain mobility was evident in the dynamics of morphological phase transitions and of related process of terrace-formation on a macroscale, as well as in the degree of long-range lateral order of nanostructures. The effect is independent of the chemical structure and on the volume composition (cylinder-/ lamella-forming) of the block copolymers. In-situ ellipsometric measurements of the swelling behavior revealed a cumulative increase in 1-3 vol. % in solvent up-take by HM-block copolymer bilayer films, so that we suggest other than dilution effect reasons for the observed significant enhancement of the chain mobility in concentrated block copolymer solutions. Another beneficial effect of the HM-support is the suppression of the film dewetting which holds true even for low molecular weight homopolymer polystyrene films at high degrees of swelling. Apart from immediate technological impact in block copolymer-assisted nanolithography, our findings convey novel insight into effects of molecular architecture on polymer-solvent interactions.Comment: This document is the unedited Author's version of a Submitted Work that was subsequently accepted for publication in Macromolecules, copyright \c{opyright} American Chemical Society after peer review. To access the final edited and published work see http://pubs.acs.org/doi/abs/10.1021/ma500561

Nano-apatite/polymer composites: mechanical and physicochemical characteristics

Hydrothermally synthesized acicular nano-apatite (Nap) was used as filler to make composites with a polyethylene glycol/poly(butylene terephthalate) (PEG/PBT) block copolymer (Polyactive™70:30). The Nap had a particle diameter of 9–25 nm and a length of 80–200 nm. The mechanical properties and the physiochemical characteristics of the composites, such as Young's modulus, swelling degree in water and the calcification behaviour, have been determined. It was found that Nap had a strong ability to promote the calcification of composites when incorporated into Polyactive 70:30, while poly(acrylic acid) (PAA) coating of Nap had an adverse effect on the calcification of composites, presumably due to the formation of complexes between PAA and PEG segments. Nap had a prominent stiffening effect for Polyactive 70:30 in the dry state, but had a poor stiffening effect for composites in an aqueous environment due to the hygroscopic nature and/or the formation of aggregates. PAA coating on Nap had almost no additional effect on the mechanical properties of composites either in the dry state or in an aqueous environment. To reinforce the polymer by Nap, achieving a more homogeneous dispersion of Nap in the polymer matrix and surface modifications to render the powders less hygroscopic appear to be necessary

Poly(dimethylsiloxane)-poly(ethyleneoxide)-heparin block copolymers. I. Synthesis and characterization

Amphiphilic block copolymers containing poly(dimethylsiloxane), poly(ethylene oxide), and heparin (PDMS-PEO-Hep) have been prepared via a series of coupling reactions using functionalized prepolymers, diisocyanates, and derivatized heparins. All intermediate steps of the synthesis yield quantifiable products with reactive end-groups, while the final products demonstrate bioactive, covalently bound heparin moieties. Due to the solvent systems required, commercial sodium heparin was converted to its benzyltrimethyl ammonium salt to enhance its solubility. The same procedure was applied to heparin degraded by nitrous acid in order to covalently couple it in solutions with the semitelechelic copolymers. As might be expected, this derivatization reduces the apparent bioactivity of the heparin. However, preliminary findings suggest that the bioactivity can be restored by reforming the heparin sodium salt

Theoretical Study of Comb-Polymers Adsorption on Solid Surfaces

We propose a theoretical investigation of the physical adsorption of neutral comb-polymers with an adsorbing skeleton and non-adsorbing side-chains on a flat surface. Such polymers are particularly interesting as "dynamic coating" matrices for bio-separations, especially for DNA sequencing, capillary electrophoresis and lab-on-chips. Separation performances are increased by coating the inner surface of the capillaries with neutral polymers. This method allows to screen the surface charges, thus to prevent electro-osmosis flow and adhesion of charged macromolecules (e.g. proteins) on the capillary walls. We identify three adsorption regimes: a "mushroom" regime, in which the coating is formed by strongly adsorbed skeleton loops and the side-chains anchored on the skeleton are in a swollen state, a "brush" regime, characterized by a uniform multi-chains coating with an extended layer of non-adsorbing side-chains and a non-adsorbed regime. By using a combination of mean field and scaling approaches, we explicitly derive asymptotic forms for the monomer concentration profiles, for the adsorption free energy and for the thickness of the adsorbed layer as a function of the skeleton and side-chains sizes and of the adsorption parameters. Moreover, we obtain the scaling laws for the transitions between the different regimes. These predictions can be checked by performing experiments aimed at investigating polymer adsorption, such as Neutron or X-ray Reflectometry, Ellipsometry, Quartz Microbalance, or Surface Force Apparatus.Comment: 30 pages, 7 figures, to be published in Macromolecule