Impact Of Polymer Structure Research Articles

Impact of polymer structure in polyurethane topcoats on anti-icing properties

Icing on the topcoat layer of structures or mobility systems can be a factor leading to functional failures or accidents. Material engineering approach to prevent icing involves creating hydrophobic surfaces. In this study, it was confirmed that the method of controlling the structure of polymers using solvents to adjust surface hydrophobicity and ice prevention effects is effective. Polyurethane (PU) topcoats are primarily used on the exterior of mobility devices; therefore, structure of PU was manipulated using xylene. Through the adjustment of the ratio between PU and xylene, changes in the curing enthalpy and crystal structure were observed, which led to alterations in tensile strength. Additionally, changes in surface energy and contact angle occurred depends on xylene content, and de-icing property of PU topcoat was enhanced by 66 % on the surface of the 20 vol% xylene PU topcoat, compared to the pure PU topcoat. It was confirmed that the basic method of manipulating the polymer structure through solvent amount in topcoats could be utilized as a technique in hydrophobic surface research, such as ice prevention.

Rheological and filtration properties of clay-polymer systems: Impact of polymer structure

In this study, the effect of polymer structure, the degree of hydrolysis, chemical structure of monomer in the backbone, and charge distribution of monomer groups on rheological and filtration properties of Bentonite (Bent)/polymer dispersions were assessed. Two different water-soluble polymers were employed to investigate the rheological and filtration properties of Bent/polymer dispersions. The polymers evaluated are a copolymer of acrylamide and 2-acrylamido-2-methylpropane sulfonic acid (AM-AMPS) (P1) and a terpolymer of acrylamide, 2-acrylamido-2-methylpropane sulfonic acid, and N-Vinylpyrrolidone (AM-AMPS-NVP) (P2). The objective of this work was to study the rheological and filtration properties of Bent/polymer dispersions in deionized and salt water at different temperatures (25 °C and 85 °C). The steady shear rheological data was fitted to Herschel-Bulkley model to compute rheological parameters like yield stress, consistency index, and flow behavior index. The incorporation of polymers in Bent dispersions improved the rheological properties of the Bent dispersions. Addition of electrolyte in Bent/polymer dispersions led to a slight decrease in the rheological properties of all developed dispersions. The Bent/P2 dispersion revealed superior rheological properties compared to the other Bent and Bent/polymer dispersions in both deionized and salt water. TEM analysis of Bent/polymer dispersions was carried out to study the morphology of dispersions. LP/LT and HP/HT filtration experiments were performed in deionized and salt water at 25 °C and 85 °C, respectively, and results showed that Bent/P2 dispersion had minimum filtrate volume and filter cake thickness compared to the Bent dispersion. The permeability of filter cakes was determined using Darcy's law and filter cake morphologies were studied using SEM analysis. The excellent rheological and filtration properties of Bent/P2 dispersion was attributed to the presence of NVP monomer group in P2 polymer, which is stable towards elevated temperatures and high salinity environments. The exceptional filtration and rheological properties of P2 polymer make it a suitable candidate for the development of high-performance drilling fluids.

Intraluminal Release of an Antifungal β-Peptide Enhances the Antifungal and Anti-Biofilm Activities of Multilayer-Coated Catheters in a Rat Model of Venous Catheter Infection.

Candida albicans is the most prevalent cause of hospital-acquired fungal infections and forms biofilms on indwelling medical devices that are notoriously difficult to treat or remove. We recently demonstrated that the colonization of C. albicans on the surfaces of catheter tube segments can be reduced in vitro by coating them with polyelectrolyte multilayers (PEMs) that release a potent antifungal β-peptide. Here, we report on the impact of polymer structure and film composition on both the inherent and β-peptide-mediated ability of PEM-coated catheters to prevent or reduce the formation of C. albicans biofilms in vitro and in vivo using a rat model of central venous catheter infection. Coatings fabricated using polysaccharide-based components [hyaluronic acid (HA) and chitosan (CH)] and coatings fabricated using polypeptide-based components [poly-l-lysine (PLL) and poly-l-glutamic acid (PGA)] both served as reservoirs for the loading and sustained release of β-peptide, but differed substantially in loading and release profiles and in their inherent antifungal properties (e.g., the ability to prevent colonization and biofilm growth in the absence of β-peptide). In particular, CH/HA films exhibited inherent antifungal and antibiofilm behaviors in vitro and in vivo, a result we attribute to the incorporation of CH, a weak polycation demonstrated to exhibit antimicrobial properties in other contexts. The antifungal properties of both types of films were improved substantially when β-peptide was incorporated. Catheter segments coated with β-peptide-loaded CH/HA and PLL/PGA films were both strongly antifungal against planktonic C. albicans and the formation of surface-associated biofilms in vitro and in vivo. Our results demonstrate that PEM coatings provide a useful platform for the design of new antifungal materials, and suggest opportunities to design multifunctional or dual-action platforms to prevent or reduce the severity of fungal infections in applied biomedical contexts or other areas in which fungal biofilms are endemic.

The impact of polymer structure on the adsorption of ionic polyamino acid homopolymers and their diblock copolymers on colloidal chromium(iii) oxide

The aim of the presented study was to investigate the influence of the structure and ionic nature of polymers on the adsorption layer architecture.

Impact of polymer structure and composition on fully resorbable endovascular scaffold performance

Fully erodible endovascular scaffolds are being increasingly considered for the treatment of obstructive arterial disease owing to their potential to mitigate long-term risks associated with permanent alternatives. While complete scaffold erosion facilitates vessel healing, generation and release of material degradation by-products from candidate materials such as poly-l-lactide (PLLA) may elicit local inflammatory responses that limit implant efficacy. We developed a computational framework to quantify how the compositional and structural parameters of PLLA-based fully erodible endovascular scaffolds affect degradation kinetics, erosion kinetics and the transient accumulation of material by-products within the arterial wall. Parametric studies reveal that, while some material properties have similar effects on these critical processes, others induce qualitatively opposing responses. For example, scaffold degradation is only mildly responsive to changes in either PLLA polydispersity or the initial degree of crystallinity, while the erosion kinetics is comparatively sensitive to crystallinity. Moreover, lactide doping can effectively tune both scaffold degradation and erosion, but a concomitant increase in local by-product accumulation raises concerns about implant safety. Optimized erodible endovascular scaffolds must precisely balance therapeutic function and biological response over the implant lifetime, where compositional and structural parameters will have differential effects on implant performance.

Exploring the mechanism of plasmid DNA nuclear internalization with polymer-based vehicles.

Cationic polymers are commonly used to transfect mammalian cells, but their mechanisms of DNA delivery are unknown. This study seeks to decipher the mechanism by which plasmid DNA delivered by a class of cationic polymers traffics to and enters the nucleus. While studies have been performed to elucidate the mechanism of naked plasmid DNA (pDNA) import into the nuclei of mammalian cells, our objectives were to determine the effects of polymer complexation on pDNA nuclear import and the impact of polymer structure on that import. We have performed studies in whole cells and in isolated nuclei using flow cytometry and confocal microscopy to characterize how polymer-DNA complexes (polyplexes) are able to deliver their pDNA cargo to the nuclei of their target cells. The polymers tested herein include (i) linear poly(ethylenimine) (JetPEI), a polyamine, and (ii) two poly(glycoamidoamine)s (PGAAs), polyamines that contain carbohydrate moieties (meso-galactarate, Glycofect (G4), and L-tartarate, T4) within their repeat units. Our results indicate that, when complexed with the PGAAs, pDNA association with the nuclei was severely hampered in isolated nuclei compared to whole cells. When the pDNA was complexed with JetPEI, there was slight inhibition of pDNA-nuclear interaction in isolated nuclei compared to whole cells. However, even in the case of PEI, the amount of pDNA imported into the nucleus increases in the presence of cytosolic extract, thus indicating that intracellular components also play a role in pDNA nuclear import for all polymers tested. Interestingly, PEI and G4 exhibit the highest reporter gene expression as well as inducing higher envelope permeability compared to T4, suggesting that the ability to directly permeabilize the nuclear envelope may play a role in increasing expression efficiency. In addition, both free T4 and G4 polymers are able to cross the nuclear membrane without their pDNA cargo in isolated nuclei, indicating the possibility of different modes of nuclear association for free polymers vs polyplexes. These results yield insight to how the incorporation of carbohydrate moieties influences intracellular mechanisms and will prove useful in the rational design of safe and effective polymer-based gene delivery vehicles for clinical use.

Nanopatterning of Plasma Polymer Thin Films by ArF Photolithography: Impact of Polymer Structure on Patterning Properties

AbstractA simple method is developed for producing patterned polymer surfaces with reactive groups. This entails pulsed plasma deposition of anhydride functionalized films, followed by the covalent attachment of an amine‐terminated nucleophile via aminolysis reaction. Patterning is achieved by deep‐UV (DUV) irradiation using an ArF excimer laser (193 nm), allowing a fabrication of periodical structures with typical dimensions ranging from the nano‐ to microscale. The impact of the duty cycle during plasma polymer deposition and the impact of amine exposure time on the DUV response are investigated. Study of the relation between the polymer structure and photosensitivity allows a deeper understanding of the photoinduced mechanisms.magnified image

Impact of polymer structure and confinement on the kinetics of Zdol 4000 bonding to amorphous‐hydrogenated carbon

The bonding of molecularly‐thin (10 A) Zdol 4000 films to amorphous, hydrogenated carbon (CHx) was investigated as a function of the Zdol structure, i.e., the ratio of the perfluoromethylene oxide (C1) to perfluoroethylene oxide (C2) monomer units in the backbone. The influence of the C1/C2 ratio on the intrinsic mobility of the Zdol polymer was also investigated by computing the energetic barriers to internal rotation about the C–O and C–C bonds in model compounds by both ab initio and molecular mechanics methods. The calculations indicate that increasing the C1/C2 ratio increases the relative flexibility of the Zdol polymer. The kinetic results demonstrate that the rate at which submonolayer Zdol films bond to CHx is non‐classical (time‐dependent) regardless of the Zdol chain stiffness. The Zdol bonding rate can best be described by a kinetic equation of the form, dB/dt=k(t)A, where the rate coefficient, k(t) can be expressed as a power function in time: k(t)= kB t -h. The values of the initial bonding rate constant, k B, and the functional form of the time dependence, t -h, are both strongly dependent on the Zdol backbone flexibility. The magnitude of the initial bonding rate constants generally increase with increasing Zdol chain mobility. A discontinuous change in both the magnitude of k B and the functional form of the time dependence is, however, observed at 64°C when the C1/C2 ratio is increased from 0.97 to 1.08. The bonding rate coefficient scales as t -0.5 for the relatively rigid Zdol backbone structures with C1/C2 < 1, while a t -1.0 time‐dependent bonding rate is observed for the more flexible Zdol backbones with C1/C2 < 1. The initial rate constant, k B, also changes abruptly near C1/C2 ≈ 1, with k B of the flexible Zdol chains (samples with C1/C2) being approximately an order of magnitude greater than the more rigid chains (C1/C2 < 1). These results indicate that the physical state of the confined Zdol film can be either liquidlike or solidlike depending upon the molecular stiffness of the backbone employed. The t -0.5 time‐dependent bonding rate is shown to be consistent with a one‐dimensional, diffusion‐limited reaction from a solidlike Zdol structure, whereas the t -1.0 bonding rate results when bonding occurs from a liquidlike Zdol film structure. The temperature dependence of the Zdol 4000 bonding rate coefficient for the Zdol backbone characterized by C1/C2 = 0.97 (solidlike at T = 64°C) was found to undergo a transition from a t -0.5 time dependence for T < 150°C, to a t -1.0 time dependence at T > 180. This transition occurs over relatively narrow temperature range (150 < T < 180°C) and is attributed to a 2D melting of the confined Zdol film.