Facile fabrication of polyethylene/silver nanoparticle nanocomposites with silver nanoparticles traps and holds early antibacterial effect

Antibacterial polyethylene (PE)/silver nanoparticle (AgNP) nanocomposites containing AgNPs at concentrations of 5 × 10^?5, 5 × 10^?4, and 5 × 10^?3 wt % were fabricated and tested. Transmission electron microscopy revealed an even dispersion of surface AgNPs in the PE/AgNP nanocomposites. No AgNP agglomeration was observed. The tensile strength, elongation at break, and Young's modulus of these PE/AgNP nanocomposites were similar to those of neat PE. Differential scanning calorimetry demonstrated that the PE/AgNP nanocomposites and neat PE had similar melting and crystallization temperatures of 126 ± 0.5 and 109 ± 0.6°C, respectively. The heats of fusion of the PE/AgNP nanocomposites containing AgNPs at concentrations of 5 × 10^?5 and 5 × 10^?4 and of 5 × 10^?3 wt % were lower than those of neat PE by 5 and 7%, respectively. These PE/AgNP nanocomposites were immersed in shaking liquid cultures of the potential pathogenic bacteria Escherichia coli, Bacillus subtilis, and Salmonella typhimurium in the lag phase. The results show that the growth rates of all of the tested bacteria were restricted effectively after 1.5, 3, and 6 h of cultivation, respectively. © 2016 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2016 , 133, 43331.     

Effects of plasma treatment on biocompatibility of poly[(L‐lactide)‐co‐(ϵ‐caprolactone)] and poly[(L‐lactide)‐co‐glycolide] electrospun nanofibrous membranes

Poly[(l ‐lactide)‐co ‐(? ‐caprolactone)] (PLCL) and poly[(l ‐lactide)‐co ‐glycolide] (PLGA) copolymers are widely used in neural guide tissue regeneration. In this research, the surface modification of their hydrophilicity was achieved using plasma treatment. Attachment and proliferation of olfactory ensheathing cells on treated electrospun membranes increased by 26 and 32%, respectively, compared to the untreated PLCL and PLGA counterparts. Cells cultivated on both the PLCL and PLGA membranes showed high viability (>95%) and healthy morphologies with no evidence of cytotoxic effects. Cells grown on treated electrospun fibres displayed significant increases in mitochondrial activity and reductions in membrane leakage when compared to untreated samples. The results suggested that plasma treatment of the surface of the polymers enhanced both cell viability and growth without incurring any cytotoxic effects. © 2017 Society of Chemical Industry     

Physical and thermal properties of l‐lactide/ϵ‐caprolactone copolymers: the role of microstructural design

Understanding the underlying role of microstructural design in polymers allows for the manipulation and control of properties for a wide range of specific applications. As such, this work focuses on the study of microstructure–property relationships in l‐ lactide/?‐caprolactone (LL/CL) copolymers. One‐step and two‐step bulk ring‐opening polymerization (ROP) procedures were employed to synthesize LL/CL copolymers of various compositions and chain microstructures. In the one‐step procedure, LL and CL were simultaneously copolymerized to yield P(LL‐stat‐CL) statistical copolymers. In the two‐step procedure, poly(l‐ lactide) (PLL) and poly(?‐caprolactone) (PCL) prepolymers were synthesized in the first step before CL and LL respectively were added in the second step to yield P[LL‐b‐(CL‐stat‐LL)‐b‐LL] and P[CL‐b‐(LL‐stat‐CL)‐b‐CL] block copolymers as the final products. The findings reveal that, in addition to the copolymerization procedure employed, the length and type of the prepolymer play important roles in determining the chain microstructure and thereby the overall properties of the final copolymer. Moreover, control over the degree of crystallinity and the type of crystalline domains, which is controlled during the polymer chemistry process, heavily influences the physical and mechanical properties of the final polymer. In summary, this work describes an interesting approach to the microstructural design of biodegradable copolymers of LL and CL for potential use in biomedical applications. © 2019 Society of Chemical Industry     

Isoconversional kinetic analysis of ring-opening polymerization of ε-caprolactone: Steric influence of titanium(IV) alkoxides as initiators

Four titanium(IV) alkoxides, namely: Ti(IV) n-propoxide (1), Ti(IV) n-butoxide (2), Ti(IV) tert-butoxide (3), and Ti(IV) 2-ethylhexoxide (4), have been used as initiators in the bulk ring-opening polymerization (ROP) of ε-caprolactone (ε-CL). The influence of the alkoxide group on the course of the ROP of ε-CL was investigated by means of ¹H-NMR and differential scanning calorimetry (DSC). The ¹H-NMR spectra confirmed that the ROP reaction of ε-CL proceeded via the widely accepted coordination-insertion mechanism for each of the four initiators. Isoconversional methods have been used to evaluate non-isothermal DSC data via the equations of Friedman, Kissinger-Akahira-Sunose (KAS) and Ozawa-Flynn-Wall (OFW). The kinetic studies showed that the polymerization rate for the four initiators (1-4) was in the order of 1 > 2 ≈ 4 > 3. The lowest activation energies (40–47, 42–44, and 49–52 kJ/mol for the Friedman, KAS and OFW methods respectively) were found in the polymerizations using Ti(IV) n-propoxide (1), while the highest activation energies (84–107, 77–87, and 80–91 kJ/mol for the Friedman, KAS and OFW methods respectively) were obtained using Ti(IV) tert-butoxide (3). Differences in the rates of polymerization and the activation energies amongst the four initiators appeared to be governed mainly by the different degrees of steric hindrance in the initiator structure. These results represent important findings regarding the steric influence of the alkoxide groups on the kinetics of the ROP of ε-CL initiated by titanium(IV) alkoxides.     

Crosslinking assisted fabrication of ultrafine poly(vinyl alcohol)/functionalized graphene electrospun nanofibers for crystal violet adsorption

This article reports the fabrication of water‐stable electrospun mats made from water‐soluble poly(vinyl alcohol) and comprising ultrafine nanofibers for a high surface area to volume ratio as required for the adsorption of crystal violet. Acid‐catalyzed crosslinking is uniquely demonstrated as a facile strategy to improve water stability and, just as importantly, fine‐tune the nanofiber size of the electrospun mats. Amine‐functionalized graphene nanoplatelets are incorporated as an adsorption performance enhancer instead of the more widely reported graphene oxide. The functionalized graphene also facilitates fabrication of the composite electrospun mats by direct mixing of the water‐dispersible graphene with the aqueous polymer solution. The enhanced adsorption performance of the polymer nanocomposite mats is explained in detail at the molecular level, while the adsorption mechanism is supported by adsorption isotherm and related kinetic data. Moreover, the adsorbent mats can be removed from the water after use with the mat integrity still maintained. © 2018 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2018 , 135, 46318.     

Application of low loading of collagen in electrospun poly[(l‐lactide)‐co‐(ε‐caprolactone)] nanofibrous scaffolds to promote cellular biocompatibility

Electrospinning of various polymers has been used to produce nanofibrous scaffolds that mimic the extracellular matrix and support cell attachment for the potential repair and engineering of nerve tissue. In the study reported here, an electrospun copolymer of l ‐lactide and ε‐caprolactone (67:33 mol%) resulted in a nanofibrous scaffold with average fibre diameter and pore size of 476 ± 88 and 253 ± 17 nm, respectively. Blending with low loadings of collagen (<2.5% w/w) significantly reduced the average diameter and pore size. The uniformity of fibre diameter distributions was supported with increasing collagen loadings. The nanofibrous scaffolds significantly promoted the attachment and proliferation of olfactory ensheathing cells compared to cells exhibiting asynchronous growth. Furthermore, analysis of cell health through mitochondrial activity, membrane leakage, cell cycle progression and apoptotic indices showed that the nanofibrous membranes promoted cell vigour, reducing necrosis. The study suggests that the use of more cost‐effective, low loadings of collagen supports morphological changes in electrospun poly[(l ‐lactide)‐co‐(ε‐caprolactone)] nanofibrous scaffolds, which also support attachment and proliferation of olfactory ensheathing cells while promoting cell health. The results here support further investigation of the electrospinning of these polymer blends as conduits for nerve repair. © 2013 Society of Chemical Industry     

Synthesis,characterization and melt spinning of a block copolymer of L-lactide and ε -caprolactone for potential use as an absorbable monofilament surgical suture

This paper describes the synthesis and characterization of a block copolymer of L-lactide (LL) and ε -caprolactone (CL) and its subsequent melt spinning into a monofilament fiber. The synthesis reaction was a two-step process. In the first step, an approximately 50:50 mol% random copolymer, P(LL-co-CL), was synthesized via bulk copolymerization of LL and CL. This first-step prepolymer then became the macroinitiator in the second-step reaction in which more LL monomer was added to form a block copolymer, PLL-b-P(LL-co-CL)-b-PLL. Both the prepolymer and block copolymer were characterized by a combination of analytical techniques comprising dilute-solution viscometry, GPC, ¹H and ¹³C NMR, DSC and TG. The block copolymer was then processed into a monofilament fiber using a small-scale melt spinning apparatus. The fiber was spun with a minimum amount of chain orientation and crystallinity so that its semi-crystalline morphology could be constructed under more controlled conditions in subsequent off-line hot-drawing and annealing steps. In this way, the fiber’s tensile properties and dimensional stability were developed, as indicated by the changes in its stress-strain curve. The final drawn and annealed fiber had a tensile strength (> 400 MPa) approaching that of a commercial PDS II suture of similar size. It is considered that this type of block copolymer has the potential to be developed further as a lower-cost alternative to the current commercial monofilament surgical sutures.     

Electrospinning polymer blend of PLA and PBAT: Electrospinnability–solubility map and effect of polymer solution parameters toward application as antibiotic‐carrier mats

Electrospinning of a biodegradable polymer blend of poly(lactic acid) (PLA) and poly(butylene adipate‐co‐terephthalate) (PBAT) is reported for the first time. Effects of several solution parameters on electrospinning are explored, including types of single and binary solvents, binary solvent mixing ratio, polymer blend concentration, polymer blending ratio, and loading content of tetrabutyl titanate as a compatibilizer. An electrospinnability–solubility map of the PLA/PBAT blend is firstly developed for the facile selection of a suitable binary solvent system, thus simplifying the laborious, time‐consuming, trial‐and‐error process. A particular binary solvent system derived from good and non‐solvent serves as the most suitable medium for the successful preparation of homogeneous bead‐free electrospun PLA/PBAT nanofibers. It is revealed that the compatibilizer acts not only as a diameter size tuner for the PLA/PBAT fibers but also as a mechanical property enhancer for the immiscible PLA/PBAT electrospun mats. Moreover, the antibacterial activity of the drug‐loaded PLA/PBAT fibrous mats suggests their potential application as antibiotic‐carrier mats. Preparation of the composite mats comprising bead‐free fibers with an average size at sub‐micrometer scale is also demonstrated, additionally promoting the possibility of using the PLA/PBAT‐based electrospun mats as a matrix of various additives for a wide range of applications. © 2018 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2018 , 135, 46486.