Surface Properties Of Poly Research Articles

Molecular Aggregation Structure and Surface Properties of Poly(fluoroalkyl acrylate) Thin Films

The effects of side chain length on the molecular aggregation states and surface properties of poly(fluoroalkyl acrylate) [PFA-Cy, where y is the fluoromethylene number of the Rf groups] thin films were systematically investigated. Spin-coated PFA-Cy thin films were characterized by static and dynamic contact angle measurements, X-ray photoelectron spectroscopy (XPS), differential scanning calorimetry, and wide-angle X-ray diffraction. The receding contact angles showed small values for PFA-Cy with short side chain (y ≤ 6) and increased for ones with y ≥ 8. It has been revealed that PFA-Cy with y ≥ 8 was crystallized and formed ordered structures. These results suggest that the water-repellent mechanism of PFA-Cy can be attributed to the presence of highly ordered fluoroalkyl chains at the outermost surfaces. The results of XPS in the dried and hydrated states and the contact angle measurement in water indicate that the contact angle for water is lowered by exposure of the carbonyl groups to the water int...

Bulk and surface modifications of polylactide

This article reviews various methods of modifying the bulk and surface properties of poly(lactic acid) (PLA) so that the polymer may be used as a drug carrier in a drug delivery system (DDS) and as a cell scaffold in tissue engineering. Copolymerization of lactide with other lactone-type monomers or monomers with functional groups such as malic acid, copolymerization of lactide with macromolecular monomer such as poly(ethylene glycol) (PEG) or dextran, as well as blending polylactide and natural derivatives and other methods of bulk modification are discussed. Surface modifications of PLA-type copolymers, such as surface coating, chemical modification, and plasma treatment are described. Cell culture technology proves the efficiency of bulk and surface modification and the potential application of PLA in tissue engineering.

Statistical analysis of the effect of dielectric barrier discharge (DBD) operating parameters on the surface processing of poly(methylmethacrylate) film

A dielectric barrier discharge (DBD) plasma, operating in air at atmospheric pressure, has been used to induce changes in the surface properties of poly(methylmethacrylate) (PMMA) films. The relative effects that key DBD operating parameters, specifically: discharge power, electrode gap and duration of exposure have on producing chemical and microstructural changes in the polymer surface region have been investigated. The approach taken involves the application of an orthogonal array experimental design and statistical analysis methodology. The various data sets obtained from these analyses have been used to develop an equation in which induced changes in the surface properties of the DBD modified PMMA films are expressed in terms of the effectiveness of the various processing parameters in producing them. In general, the results obtained clearly indicate that DBD plasma processing is an effective method for the controlled surface modification of PMMA. Relatively short exposures to the atmospheric pressure discharge produces a significant amount of oxygen incorporation at the surface as indicted by a pronounced reduction in water contact angle. Analysis of the role of each of the operating parameters concerned shows that they do indeed have selective effectiveness for inducing resultant surface modification. Duration of exposure to the DBD plasma, expressed here as the number of treatment cycles at a given speed of specimen transit through the electrode gap, was found to play a major role in decreasing the surface wettability of PMMA. Conversely, the magnitude of the discharge power was not a significant parameter in this regard. In contrast, the value of the applied power played the dominant role in achieving the observed enrichment of the surface oxygen abundance, as measured by XPS, with the duration of exposure to the discharge playing a secondary role in this case. The nature and scale of the induced surface changes that originate from the various processing conditions employed have been further considered to determine if an interrelationship exists between them. Non-parametric data analysis indicates that no significant correlation exists between the observed changes in measured polymer wettability and the attendant surface oxygen enrichment. This result suggests that the increase in surface wettability caused by DBD processing, as manifested in a reduced contact angle, is not merely attributable to changes in the surface chemistry. As such, it is postulated that changes in the surface microstructure may also contribute to this change in surface wettability.

Thermoresponsive Poly(N-isopropylacrylamide) Copolymers: Contact Angles and Surface Energies of Polymer Films

Surface properties of poly(N-isopropylacrylamide) (PNIPAM) copolymer films were studied by contact angle measurements and optical and atomic force microscopy. We prepared a series of copolymers of N-isopropylacrylamide with N-tert-butylacrylamide (NtBA) in order of increasing hydrophobicity. The measurements of the advancing contact angle of water at 37 degrees C were hampered by the observation of a distinct stick/slip pattern on all polymers in the series with the exception of poly(NtBA) (PNtBA). We attributed this behavior to the film deformation by the vertical component of liquid surface tension leading to the pinning of the moving contact line. This was confirmed by the observation of a ridge formed at the pinned contact line by optical microscopy. However, meaningful contact (without the stick/slip pattern and with a time-independent advancing contact angle) angles for this thermoresponsive polymer series could be obtained with carefully selected organic liquids. We used the Li and Neumann equation of state to calculate the surface energy and contact angles of water for all polymers in the series of copolymers and van Oss, Chaudhury, and Good (vOCG) acid-base theory for PNtBA. The surface energies of the thermoresponsive polymers were in the range of 38.9 mJ/m2 (PNIPAM) to 31 mJ/m2 (PNtBA) from the equation of state approach. The surface energy of PNtBA calculated using vOCG theory was 29.0 mJ/m2. The calculated contact angle for PNIPAM (74.5 +/- 0.2 degrees ) is compared with previously reported contact angles obtained for PNIPAM-modified surfaces.

Surface Properties of Poly(3-hydroxybutyrate-co-3- hydroxyvalerate) Banded Spherulites Studied by Atomic Force Microscopy and Time-of-Flight Secondary Ion Mass Spectrometry

Banded spherulites of poly(3-hydroxybutyrate-co-3-hydroxyvalerate) (P(3HB-3HV)) random copolymer were prepared by isothermal crystallization at 90 °C for 10 h. Using tapping-mode atomic force microscopy (AFM), the concentric periodic ridges and valleys on the surface of the banded spherulites of this polymer were found to consist of edge-on and flat-on lamellae, respectively. The periodic concentric ridges and valleys observed by AFM corresponded to the periodic extinction rings observed by polarized optical microscopy. AFM measurements showed that the interaction between the AFM probe and the sample surface can be significantly influenced by lamellar orientation.

Surface properties of poly(acrylonitrile) (PAN) precipitation polymerized in supercritical CO 2 and the influence of the molecular weight

In this paper, the surface properties, e.g., the total surface free energy and the related Lifshitz–van der Waals and Lewis acid–base components, of polyacrylonitrile (PAN) precipitation polymerized in supercritical CO 2 have been characterized. Moreover, the influence of molecular weight varying has been also investigated. Results show that the surface properties of PAN resulting from supercritical CO 2 are different from those obtained by the conventional method. Of these data, one important finding is that the supercritical CO 2 PAN seems to decrease the surface free energy with the increased molecular weight. Based on previous recorded NMR spectra of this PAN and especially compared to commercial PAN, such phenomena are discussed and ascribed to an increase of the H-bonds and a reduction of the isotacticity in the supercritical CO 2 condition for PAN.

Surface properties of poly( N-monoalkylmaleamic acid-alt-styrene) sodium salts: effect of the molecular weight and the side chain length

The surface properties of poly( N-monoalkylmaleamic acid-alt-styrene) sodium salts are studied as a function of the molecular weight and the size of the linear alkyl lateral chain of the polyelectrolyte. The experimental results are well described by the Gibbs–Szyszkowski treatment. Both the surface tension behavior and the standard free energy of adsorption depend on the polyelectrolyte side chain and on the average molecular weight, M w . An M w -dependent contribution to the free energy of adsorption ranging from −1.21 to −1.05 kJ for mole of methylene groups is found. The area covered by monomer units increases with M w and the sizes of side chains are similar to those reported in small-molecule systems. The nature of the functional group amide in the side chain has practically no effect on the surface properties as compared with the ester group in this kind of polyelectrolytes.

Influence of poly(methyl methacrylate) impregnation ratio on the surface properties of fumed silica and on the glassy temperature of poly(methyl methacrylate) using inverse gas chromatographic analysis

The surface properties of poly(methyl methacrylate) (PMMA) impregnated fumed silicas, in a large range of impregnation ratios, were examined using inverse gas chromatography at infinite dilution. It was observed that the dispersive component γ s d does not decrease monotonously with the impregnation ratio. Two critical coverage ratios were evidenced corresponding at first to the shielding of the most energetic sites and then to the achievement of total coverage of the silica surface. The influence of the coverage ratio on the glassy temperature ( t g) of the adsorbed PMMA was also studied, which was evidenced down to a very low coverage ratio (1 monomer unit/nm 2).

Production of asymmetric track membranes with a high permeability and separation selectivity

An investigation of the structure and surface properties of poly(ethylene) terephthalate track membranes (PET TM) with a changed pore profile subjected to the plasma RF-discharge is performed. It was arranged that effect of the non-polymerizing gas plasma on the membranes of researched sample leads to formation of asymmetric membranes possessing a higher flow rate. Choice of optimal discharge parameters allows one to etch the membrane in its layer. In this case in the membrane layer not affected by plasma, the mean pore diameter remains at its initial level. Preserving the initial (nominal) pore diameter allows one to perform the filtration processes with no decrease of separation selectivity. It is shown that the introducing of the polymerizing gas, cyclohexane, into the composition of plasma-forming gas provides improved hydrodynamic properties of asymmetric membranes.

Enhanced cell affinity of poly ( d, l-lactide) by combining plasma treatment with collagen anchorage

Surface properties of poly ( d, l-lactide) (PDLLA) were modified by combining plasma treatment and collagen modification. The changes of surface properties were characterized by contact angles, surface energy, X-ray photoelectron spectra and scanning electron microscopy. The mouse 3T3 fibroblasts were used as model cells to evaluate the cell affinity of PDLLA before and after modification. Effects of different modification methods including plasma treatment, collagen coating and combining plasma treatment with collagen anchorage were investigated and compared. The results showed that the hydrophilicity and surface-free energy were improved and reduced, respectively, after each modification. Plasma pre-treatment could improve the roughness as it incorporated the polar groups and positively charged groups onto the sample surface; so the plasma pre-treated surface would benefit in anchoring more collagen tightly. As a result, cell affinity of PDLLA modified by combining plasma treatment with collagen anchorage was greatly improved. The modified materials could endure rinsing by PBS, which would facilitate further application when the modified materials were used as cells scaffold in tissue engineering.

Size-dependent Thermosensitivity of Poly (N-isopropylacrylamide-co-acrylic acid) Hydrogel Microspheres Prepared by a Membrane Emulsification Method: Phase Transition Temperature Changes Depending on the Hydrogel Size.

Changes in the surface properties of poly (N-isopropylacrylamide-co-5mol% acrylic acid) microspheres depending on tempereture and the size of the microspheres were studied by measuring the electrophoretic mobility of the microspheres in electrolyte solutions at pH7.4 at 25, 30, 33, 35, 40, and 45°C. The hydrogel microspheres were monodisperse, since they were prepared from w/o emulsion using a membrane emulsification method. The size of the microspheres was dependent on the membrane pore size of the membrane. Membranes with four pore sizes ware used. Poly (N-isopropylacrylamide-co-5mol% acrylic acid) microspheres have shown negative electrophoretic mobility values. More megative values were obtainde with the smaller microspheres than the larger ones at each temperature. The surface became harder as temperature rose, independent of the microsphere size. This is caused by the shrinkage of poly (N-isopropylacrylamide) moiety, LCST of which is 33°C. It has been newly found that the smaller microspheres have a lower phase transition temperature (LCST) and exhibit the stronger dependence of surface charge density on the temperature than the larger ones. The surface charge density of the microspheres became higher only in the small microspheres as temperature rose, and it changed little in larger microspheres. That is, in the case of poly (N-isopropylacrylamide-co-5mol% acrylic acid) hydrogels, thermosensitive changes of their surface strcutures are dopendent on their size, because the hetrogeneity of the microsphere structural is different depending on their sizes. These observations suggest that the changes on structural heterogeneity of poly (N-isopropylacrylamide-co-5mol% acrylic acid) microgels affect their LCST and that the heterogeneous gel structure of microgels strongly affects their surface properties as comparing with those of bulk gels

Alteration of surface properties of poly(1-(trimethylsilyl)-1-propyne) by direct-current discharge treatment

The effect of direct-current discharge treatment in air on alteration of surface properties (contact angle, surface charge density, and chemical structure of polymer) of poly(trimethylsilylpropyne) was investigated. Substantial hydrophilization of the polymer is primarily associated with high density of a negative surface charge due to trapping of electrons injected from a plasma

Association and Surface Properties of Poly(ethylene oxide)−Poly(styrene oxide) Diblock Copolymers in Aqueous Solution

The association and surface properties of three oxyethylene/oxyphenylethylene (ES) diblock copolymers in aqueous solution have been studied. Copolymers E50S3.5, E50S5.1, and E51S6.5 were synthesized and characterized by gel permeation chromatography and 13C NMR spectroscopy. Surface tensiometry was used to determine critical micelle concentrations (cmc) at several temperatures, and thereby values of the enthalpy of micellization (ΔmicHo). The values of cmc and ΔmicHo were found to be low (e.g., 0.03 g dm-3 at 30 °C and 12 kJ mol-1 for E51S6.5), which is consistent with the high hydrophobicity of oxyphenylethylene block. Dynamic and static light scattering were used to characterize the micelles in dilute solution, yielding micellar association number, hydrodynamic and thermodynamic radius, and the related thermodynamic expansion factor. At higher concentrations, solution of copolymers E50S5.1 and E51S6.5 formed hard isotropic gels.

The versatile surface properties of poly(cyclopentadiene)-modified silica particles (PCPD-silica): XPS and electrokinetic studies

Surface properties of poly(cyclopentadiene)–silica hybrid particles (PCPD–silica) were studied by means of XPS and electrokinetic measurements. The surfaces of PCPD–silica particles exhibit two different areas with different properties: bare silica holes and PCPD patches. The PCPD chains contain different functional groups such as alcohol and carbonyl groups that were identified by XPS. The PCPD chains are grafted covalently onto the silica surface via Si–O–C bonds created by the reaction of silanol groups and active PCPD chains. The amount of Si–O–C was examinated by means of XPS. The Bronsted acidity of the residual silanol groups was determined by means of electro-kinetic measurements. It was found that the pK a values of the residual silanol groups increase with increasing polymer content on the particle surface. The surface acceptor strengths of the hybrid particles in non-aqueous liquids were investigated by the solvatochromic indicator bis(1,10-phenanthroline)-cis-dicyano-iron-II in 1,2-dichloroethane.

Adsorption of albumin, collagen, and fibronectin on the surface of poly(hydroxybutyrate-hydroxyvalerate) (PHB/HV) and of poly(ε-caprolactone) (PCL) films modified by an alkaline hydrolysis and of poly(ethylene terephtalate) (PET) track-etched membranes

The effect of alkaline hydrolysis on several surface properties of poly(hydroxybutyratehydroxyvalerate) (92/8) (PHB/HV) and poly(ε-caprolactone) (PCL) films and of poly(ethylene terephtalate) (PET) track-etched membranes have been characterized, as well as the adsorption of three proteins normally encountered by mammalian cells in vivo, namely albumin, collagen, and fibronectin. The water contact angle decreases and the number of -COOH functions accessible to a chemical reaction at the surface of PCL increases with alkaline hydrolysis. Analysis by atomic force microscopy pictures reveals a change in surface morphology. The modifications of surface properties are correlated with a two times increase of the adsorption of three radiolabelled proteins. The hydrolysis results in a slight increase in the water contact angle of one face of the PHB/HV film and a sharp increase in the number of -COOH functions. Important morphology changes are also induced. The adsorption of the radiolabelled proteins is almost 100 times higher on the hydrolyzed polymer than on the native surface. The increase in hydrophilicity of different PET batches correlates to an increase in the number of -COOH functions. Nevertheless, the surface chemical composition and rugosity are constant and no significant difference in the amount of radiolabelled fibronectin adsorbed on the different surfaces is detectable. In conclusion, the effect of hydrolysis on the surface properties of each of the polyesters studied as well as the proteins adsorption on the different surfaces are different. The results strongly support the hypothesis that, in the system studied, parameters other than hydrophilicity influence protein adsorp

Blends of polycaprolactone-poly(dimethylsiloxane)-polycaprolactone triblock copolymer with poly(vinyl chloride): preparation and characterization

Miscibility, thermal, mechanical, gas permeation, morphological and surface properties of poly(vinyl chloride) (PVC) blends containing 1–10% triblock polycaprolactone—poly(dimethylsiloxane)—polycaprolactone (PCL-PDMS-PCL) copolymer were investigated by using several techniques. Fourier transform infra-red analysis of blends reveal the existence of specific interactions via hydrogen bonding between the α-hydrogen of PVC and the carbonyl group of PCL in the triblock copolymer. This PCL-PDMS-PCL/PVC blend system exhibited a single glass transition according to differential scanning calorimetry and dynamic mechanical thermal analysis results. Stress—strain results showed that PCL-PDMS-PCL triblock copolymer is a very effective plasticizer for PVC. Gas permeability of the blends increased with the copolymer content. Morphological and surface properties of the blend system were examined by scanning electron microscopy and contact angle measurements.

Influence of CO2 laser radiation on the surface properties of poly(ether ether ketone)

The influence of CO2 laser radiation on the surface properties of poly(ether ether ketone) (PEEK) is shown. The influence on the surface chemistry is nearly negligible, but the roughness increases and the crystallinity in the surface region decreases with increasing laser intensity. The crystallinity of the surface region was determined by a newly developed procedure using photoacoustic infrared spectroscopy. © 1997 John Wiley & Sons, Inc. J Appl Polym Sci 64: 1091–1096, 1997

Surface properties of poly(ethylene imine)-coated mica surfaces—salt and pH effects

The adsorption of a branched weak polybase, poly(ethylene imine) (PEI), on the basal plane of muscovite mica was investigated using surface force measurements, electro-osmotic measurements, and ESCA. The use of this combination of techniques allows us to obtain information about adsorbed amount, interfacial charges, average structure of adsorbed layers and the most important types of forces acting between PEI-coated surfaces. The system was studied under two different conditions. The adsorbed layer adopts a flat conformation at low ionic strength and at low pH owing to the predominance of electrostatic forces. The interfacial properties of PEI-coated surfaces are compared with those of strong polyelectrolytes as well as with a linear weak polybase studied previously under similar conditions. At higher pH-values the adsorbed amount increases owing to a reduction in the polyelectrolyte charge density. This results in a thicker layer and in the increased importance of repulsive steric forces. Finally, the interaction between one polyelectrolyte-coated surface and a bare mica surface was investigated and compared with recent theoretical predictions.

Scratch hardness studies of poly(ether ether ketone)

This paper describes a study of the surface properties of poly(ether ether ketone) (PEEK) using a scratch hardness technique. A comparison of the scratch friction and the hardness values determined for amorphous and semi-crystalline PEEK shows that the crystalline polymer is harder. Studies carried out on PEEK treated with chloroform indicate that this organic solvent induces plasticization in PEEK evidenced by a change in the frictional properties and a decrease in hardness. Also, blending PEEK with other polymers, poly(ether imide) (PEI) and polytetrafluoroethylene (PTFE), demonstrates that the degree of crystallinity in PEEK is increased by the presence of such polymers.

Changes in charge density and softness of a poly( l-lactide) microcapsule surface in the hydrolytic degradation process

The changes in surface properties of poly( l-lactide) microcapsules caused by hydrolytic degradation have been studied with electrophoretic mobility measurements. An electrokinetic model has been applied to examine the electrophoretic mobility data, which were previously analyzed with a model that does not take into account the liquid flow inside the microcapsule membrane [K. Makino, H. Ohshima and T. Kondo, J. Microencapsulation, 4 (1987) 47]. The present new model involves two parameters, the charge density in the microcapsule membrane and a softness parameter, the latter of which characterizes the reciprocal of the frictional coefficient of the polymer exerted on the liquid flow. Information about the changes in charge density and in the softness of the poly( l-lactide) microcapsule surface have been newly obtained. The surface charge density increases by the cleavage of ester bonds in the polymer chain in the initial stage of the degradation process. It then gradually decreases down to the value for intact poly( l-lactide) microcapsules as a result of the release of degraded polymer segments from the microcapsule surface. Also, as the degradation proceeds, the softness parameter value increases, suggesting that the surface of the microcapsules becomes softer, probably because the surface becomes porous. The above change in the softness and the decrease in charge density at the later stage of the degradation both imply liberation of charged polymer segments. The degradation of poly( l-lactide) microcapsules proceeds by alternate repetition of cleavage of the ester bonds in the polymer chains and liberation of the degraded polymer segments from the surface.