Surface Of Cast Films Research Articles

Comparative study of physical and chemical properties of PLA-based films obtained by solution casting and flat-slot die melt extrusion

In this study the effect of processing methods on physical and chemical properties of polylactide (PLA) (Mn 130 kDa, L-93/ D-7) was investigated. PLA-films were obtained by solution casting and melt extrusion using Bestfiilament extruder equipped with flat-slot die. SEM, AFM, FTIR-spectroscopy and DSC were used for characterization of the films. The films obtained by flat-slot die melt extrusion had a relief surface with prominent strands and inclusions, while the cast films had a smooth surface with pores or gaps ranging in size from 20 to 60 μm. The average roughness (Ra) and root-mean-square roughness (Rq) of the surface of cast films were at the level of 45-48 and 37-39 nm, respectively. Meanwhile, for the melt films these values increased and corresponded to 122 and 65 nm, respectively. According to FTIR, both types of films were characterized by an increase in the absorption peaks at 1800-1700, 1450-1470 and 1350-1320 cm-1, which correspond to stretch vibrations of ester bond and bending vibrations of the C-H bond, respectively. DSC data showed decrease in crystallinity of PLA and change in its internal structure from amorphous-crystalline to amorphous after the processing.

Influence of casting solvent on phenyl ordering at the surface of spin cast polymer thin films

Controlling the surface molecular structure of spin cast polymer films is important for the rational design of surface properties. However, the relationship between spin casting parameters and film surface molecular structure is poorly understood. We report that the surface molecular structure of spin cast homopolymers which contain phenyl groups is influenced by the solvent aromaticity, investigated by a nonlinear optical spectroscopy, sum frequency generation (SFG) vibrational spectroscopy. When phenyl groups were located in a linear polymer backbone, spin casting with aromatic solvents enhanced the phenyl SFG signal relative to when a non-aromatic solvent was used which suggests that the aromatic solvent induced the surface phenyl groups to be more ordered and/or to lie more perpendicular to the film surface. In addition, when alkyl structures were believed to be present at the solvent/air interface, alkyl structures were observed at the film/air interface which suggests that molecular structure at the solvent/air interface was carried to the film surface. The effects of solvent aromaticity on phenyl ordering at spin cast film surfaces can be explained by different molecular structures of polymer chains at solvent/air interfaces, preferential solvation of functional groups during evaporation, and re-orientation of bulky side groups at the polymer film/air interface.

Synthesis, Characterization, and Surface Morphology of Pendant Polyhedral Oligomeric Silsesquioxane Perfluorocyclobutyl Aryl Ether Copolymers

The synthesis and characterization of solution processable, semi-fluorinated perfluorocyclobutyl (PFCB) aryl ether polymers possessing covalently bound pendant polyhedral oligomeric silsesquioxanes (POSS) cages is reported. The synthesis of POSS aryl trifluorovinyl ether (TFVE) monomers was accomplished by the condensation of commercial monosilanolalkyl-POSS with a TFVE-functionalized chlorosilane. POSS TFVE monomers were elucidated by 1H, 19F, 13C, and 29Si NMR spectroscopy, ATR-FTIR analysis, and elemental (C, H, and F) combustion analysis. Bulk thermal copolymerization of POSS TFVE monomers afforded random and block PFCB aryl ether copolymers functionalized with various POSS loadings. Quantitative monomer conversion was monitored by 19F NMR, which produced copolymer number-average molecular weights (Mn) of (19.5−24.9) × 103 (in CHCl3 using polystyrene as standard) determined by gel permeation chromatography (GPC). Thermal properties of POSS PFCB aryl ether copolymers were evaluated by differential scanning calorimetry (DSC) and thermal gravimetric analysis (TGA). Transmission electron microscope (TEM) analysis of spin cast optically transparent, flexible POSS PFCB aryl ether copolymer films revealed the presence of 5−20 nm-sized POSS agglomerates. Optical profilometer analysis of spin and drop cast film surfaces exhibited a modest increase in surface roughness of POSS PFCB aryl ether copolymers as compared to PFCB aryl ether homopolymers without POSS inclusion. The POSS copolymers exhibited a modest increase in hydrophobicity as measured by static water contact angle analysis. Synthesis, characterization, thermal analysis, and unique surface features of POSS PFCB aryl ether copolymers are discussed.

Biocompatible and biodegradable phosphorylcholine ionomers with reduced protein adsorption and cell adhesion

In this paper a recently developed biodegradable phosphorylcholine ionomer (PC ionomer) was evaluated in different biological environments with a focus on the adsorption of proteins (fibrinogen) and the adhesion of cells. Our results have shown that the polar phosphoryl choline (PC) group may be enriched at the surface of cast films with an added hydrophilic environment. X-ray photoelectron spectroscopy confirmed the surface depletion of PC groups in dry conditions, as nitrogen and phosphorous atoms were found in the bulk of the material but not at the outermost surface layer. The surface enrichment leads to a strongly hydrophilic surface that prevents the adsorption of proteins and reduces the adhesion of cells. The non-functional and hydrophobic reference poly(trimethylene carbonate) (PTMC) adsorbs both proteins and cells, thus the wetting and low adhesion behavior of the PC ionomer can be attributed to the introduced PC functionality. Since the in vivo acceptance of biomaterials is determined by their ability to withstand protein adsorption the PC ionomer described in this paper is highly interesting for a number of in vivo applications in which the adsorption of proteins may be critical, for example, blood contact events.

Phosphoryl Choline Introduces Dual Activity in Biomimetic Ionomers

Dual activity of phosphoryl choline (PC) functional poly(trimethylene carbonate) (PTMC) was found which induces the zwitterionic biomimetic PC group to form physical cross-links with ionomers in the bulk, and at the same time enrich at the surface of cast films. The formation of zwitterionic domains from a bifunctional PC-PTMC-PC (ionomer) provided firm films with a low elastic modulus in contrast to the tacky PTMC starting material (Mn approximately 3900 g/mol) with poor mechanical performance. In addition, the ionomer possessed improved hemocompatible properties that was explained by the enrichment of PC at the surface, suggesting a way to tailor the mechanical performance of biodegradable PTMC-based ionomers while providing its bioactivity. Tailored elasticity while maintaining hemocompatibility of a biodegradable ionomer should be of particular interest for a variety of in vivo applications.

Oxidative Degradation of trans‐1,4‐Polyisoprene Cast Films and Single Crystals by Enzyme‐Mediator Systems

AbstractDepolymerization and morphological changes of cast films and single crystals of trans‐1,4‐polyisoprene with three enzyme‐mediator systems, lipoxygenase/linoleic acid (LPO/LH), horseradish peroxidase/1‐hydroxybenzotriazole (HRP/1‐HBT) and laccase/1‐hydroxybenzotriazole/linoleic acid (laccase/1‐HBT/LH), were investigated by scanning electron microscopy and gel permeation chromatography. Treatment of cast film with a LPO/LH system involving radical generation via lipid peroxidation led to a marked decrease in the molecular weight of polymers. LPO/LH system resulted in the morphological damage of single crystals of trans‐1,4‐polyisoprene. Laccase/1‐HBT/LH also destroyed the single crystals and depolymerized emulsified trans‐1,4‐polyisoprene. On the contrary, spherulites appeared on the surface of cast films and the molecular weight slightly decreased after treatment with HRP/1‐HBT, indicating that the amorphous region was predominantly degraded and the crystal region remained unchanged. The morphology of single crystals remained unchanged during the treatment of HRP/1‐HBT system for 6 d. In addition, Fenton reagent/linoleic acid was used as a chemical initiator of lipid peroxidation for degradation of trans‐1,4‐polyisoprene cast films. This system reduced molecular weight of the cast films, as well as LPO/LH system.Scanning electron micrographs of trans‐1,4‐polyisoprene single crystals before (A) and after (B) treatment with the lipoxygenase/linoleic acid system.magnified imageScanning electron micrographs of trans‐1,4‐polyisoprene single crystals before (A) and after (B) treatment with the lipoxygenase/linoleic acid system.

Polyethylene grafted maleic anhydride to improve wettability of liquid on polyethylene films

Blends of linear low density polyethylene (LLDPE) and LLDPE grafted maleic anhydride (LLDPE-g-MA) were prepared by melt mixing. The surface of cast films with different contents and types of maleated PE were characterized through contact angle and wetting tension measurements, as well as attenuated total reflection IR spectroscopy. The tensile properties and light transmission of extruded films, as well as the performance of these films compared with commercial “antifog” films, for greenhouses were determined. The carbonyl polar groups on the surface of LLDPE/LLDPE-g-MA blends increased, and the equilibrium contact angles of water and dimethylformamide decreased when the content of maleated PE increased. Films made with these blends showed a noticeable reduction in water drop formation as the MA content was increased and when using LLDPE-g-MA of lower molecular weight. The light transmission through these films under condensation was improved when using increased contents of MA, which promotes better wetting of the water on the surface. © 2001 John Wiley & Sons, Inc. J Appl Polym Sci 79: 1802–1808, 2001

Improved Thin Film Transistor (TFT) performance using fractionated Poly-3-hexylthiophene (P3HT)

ABSTRACTBy using the Trznadel method, it has been possible to increase molecular weight, the regio-regularity, and probably to decrease the residual catalyst of poly-3-hexylthiophene thin films. The drift mobility of holes, normal to the surface of cast films, in air, has been found using Schottky diodes, and field-effect mobility has been measured with Thin-Film Transistors. Three types of film have been studied using the two methods of assessing mobility. The as-synthesised films are compared with those that have been fractionated. The third set of films involves doping with 2,3-dichloro-5,6-dicyano-1,4-benzoquinone (DDQ). The doped films show a field effect mobility of 0.2 cm2V-1s-1: all others being lower. Field effect mobility is approximately two orders of magnitude greater than that in the bulk normal to the plane of the film. Doping levels in the films are found to be similar, probably because of the process conditions.

Anticoagulant surface prepared by the heparinization of ionic polyurethane film

We present a new method for heparinization on the surface of polyurethane. The segmented polyurethane was first modified with an epoxide monomer and followed by a ring-opening reaction with diethanolamine to introduce sufficient hydroxyl groups on the surface of cast film. On this film surface, a cationic monomer was grafted by using tetravalent Cerium salt as an initiator. Heparin was immobilized in high efficiency on the ionized surface through static interactions in aqueous solution. The structure of ionized and heparinized surfaces were characterized by attenuated total reflectance infrared spectroscopy (ATR–FTIR) and electron spectroscopy for chemical analysis (ESCA) spectra. The platelet-rich plasma (PRP) contacting test and the platelet-poor plasma (PPP) clotting time measurements showed that the immobilized heparin retained its strong anticoagulant property. The release of heparin from film into salt solution was also studied, and it was found that only a small portion of heparin (10–20%) was released over a period as long as 10 h. It is expected that this new method for surface heparinization can be used to prepare antithrombogenic materials with long-term stability. © 2000 John Wiley & Sons, Inc. J Appl Polym Sci 76: 382–390, 2000

Polypropylene/polypropylene-grafted acrylic acid blends for multilayer films: Preparation and characterization

Polypropylene (PP) was functionalized with acrylic acid (AA) and styrene (st) as a comonomer by means of a radical-initiated melt-grafting reaction. FTIR, ESCA, and 1H-NMR spectroscopies were used to characterize the formation of polypropylene grafted with acrylic acid (PP-g-AA) and polypropylene grafted with acrylic acid and styrene (PP-g-AAst). The content of AA grafted onto PP was determined by using volumetric titration. Blends of PP with 0–100 wt % of PP-g-AA were prepared by melt mixing. The effect of the modified polymer content on the surfaces of cast films was characterized through FTIR–ATR and ESCA analysis as well as contact-angle, wetting-tension, and ink-adhesion measurements. The influence of the content of AA on the melting and crystallization temperature of PP was investigated by DSC. The contact angles of water on cast-film surfaces of PP/PP-g-AA blends decreases with increasing modified polymer content and decreasing PP-g-AA molecular weight. A notorious improvement on wetting tension was observed with increasing modified polymer content and decreasing PP-g-AA molecular weight. From FTIR–ATR and ESCA spectra of the blends, a calculation was made of the carbonyl index on the films' surfaces. It was found that the higher the carbonyl index, the lower the contact-angle value for the polypropylene blends. An increase in crystallization temperature of PP was observed when AA monomers were grafted into PP and with increasing PP-g-AA content in the blend, probably caused by a nucleation effect of AA monomers that would improve the crystallization capability of PP. © 2000 John Wiley & Sons, Inc. J Appl Polym Sci 79: 1497–1505, 2001

Performance of polyethylene/ethylene‐vinyl alcohol copolymer/polyethylene multilayer films using maleated polyethylene blends

AbstractBlends of linear low density polyethylene (LLDPE) and linear low density polyethylene grafted with maleic anhydride (LLDPE‐gMA) were used to promote adhesion between LLDPE and ethylene‐vinyl alcohol copolymer (EVOH) in a coextruded three layer flat film, trying to avoid the use of a tie layer. These particular films could be an option when the equipment for a five layer system is not available. The effect of the modified polymer on the surface of cast films was characterized through contact angle measurements. T‐peel strength, and oxygen and water vapor transmission rate of the multilayer films were measured as a function of LLDPE‐gMA content. Compressed films with 0%, 0.03%, and 0.08% of maleic anhydride (MA) were also analyzed by infrared spectroscopy (FTIR). The increased T‐peel strength observed when using MA contents higher than 0.08% suggests a good interfacial adhesion between layers. This increase could be associated with specific interactions between the LLDPE‐gMA and the EVOH, as the development of covalent bonds through the reaction of the anhydride with the EVOH hydroxyl groups across the interface. This was proved by the FTIR analysis that showed an increase in the ester band absorbance with an increase on the maleated polymer content and bonding time indicating that a chemical reaction occurred, at the interface. The observed changes on the oxygen and water vapor barrier properties of the films were not significant.

Characterization of amorphous domains in cellulosic materials using a FTIR deuteration monitoring analysis

We have attempted to develop a technique to characterize the amorphous or non-crystalline regions in cellulosic materials using Fourier transform infra-red spectroscopy to monitor the deuteration process for a film sample, followed by a subsequent kinetic analysis. It is possible that the H–D exchange reaction rate for OH groups in the films may reveal the nature or extent of the amorphous regions. The morphological contribution of the film surface to the analysis was determined using atomic force microscopy for both cast and coagulated cellulose films. The results showed that the surface of cast films are much rougher than that of coagulated ones. However, during the initial 5min of the deuteration process, both types of films gave similar values for the D2O diffusion coefficient, indicating that the differences in the cellulose film surfaces did not have a significant effect on the D2O penetration diffusion rate. Next we examined whether the OH–OD exchanging rate, which was found to exhibit pseudo-first-order kinetics, could or could not be used to comment on the nature or extent of amorphous regions present in the films. We also examined the relationship, if any, between the exchange rate and the diffusion coefficient. Other amorphous cellulosic films, composed of regioselectively methylated cellulose, such as 2,3-di-O-methylcellulose (23MC) and 6-O-methylcellulose (6MC) were also studied and the results were compared with the cast and coagulated films of pure cellulose. The results indicated that the non-crystalline phase of cellulosic films are not composed solely of homogeneous domains nor are they totally amorphous but rather they were found to have a heterogeneous organization.

Anisotropic ionic conductivity of lithium-doped sulfonated PBI

The conductivity study results of lithium-doped sulfonated PBI, a conjugated rigid rod polymer, poly[(1,7-dihydrobenzo[1,2-d:4,5-d′]dimidazole-2,6-diyl)-2-(2-sulfo)-p-phenylene], derivatized with pendants of propane sulfonate Li+ ionomer are reported. The room-temperature DC four-probe conductivity parallel to the surface of cast films was as large as 8.3 × 10−3 S/cm. Similar measurements with an eight-probe configuration showed no difference between bulk and surface conductivity. The ionic nature of the conductivity was indicated by constant voltage depletion experiments and by secondary ion mass spectroscopy measurements of the residues near the electrodes. The DC two-probe conductivity measured transverse to the sample surface was three to four orders of magnitude smaller than longitudinal conductivity, while the AC two-probe conductivity was even less. Electron microscopy indicated that the films had a layered structure parallel to the surfaces. This structural anisotropy was confirmed by refractive index values obtained from wave-guide experiments and by wide angle X-ray scattering. © 1997 John Wiley & Sons, Inc. J Polym Sci B: Polym Phys 35: 2925–2933, 1997

Characterization of LLDPE-LLDPEgMA Blends by Contact Angle and FTIR-ATR Studies

Blends of linear low-density polyethylene (LLDPE) and linear low density polyethylene-grafted maleic anhydride (LLDPEgMA) were prepared by melt mixing. The surface of cast films with overall contents of 0 to 100 wt% of maleated LLDPE were characterized through contact angle measurements as well as attenuated total reflection infrared spectroscopy (FTIR-ATR). The contact angles of water and dimethylformamide (DMF) on cast film surfaces of LLDPE/LLDPEgMA blends decreases when the modified polymer content increases. From FTIR-ATR spectras of the blends, the carbonyl index on the films' surface was calculated. It was found that the higher the carbonyl index, the lower the contact angle value for the polyethylene blends. The roughness of the cast and extruded reference films was also analyzed using atomic force microscopy (AFM).

Difference in adhesion and proliferation of fibroblast between Langmuir-Blodgett films and cast surfaces of poly (gamma-benzyL L-glutamate)/poly(ethylene oxide) diblock copolymer.

Block copolymers consisting of poly (gamma-benzyl L-glutamate) and poly (ethylene oxide) as the hydrophobic and hydrophilic components, respectively were prepared. Cell attachment onto the surfaces of block copolymers fabricated either as well-defined ordered Langmuir-Blodgett (LB) films or solvent cast microphase-separated structures was studied. On ordered LB surfaces, adherent fibroblasts were larger than on the microphase-separated cast surfaces within 15 min. The difference in cell adhesion between LB films and cast surfaces increased with increasing PEO contents in block copolymer. Adherent cells increased with an increase in surface pressure of LB films in any polymer. Phase-contrast microphotographs of adherent cells showed rapid and extensive morphologic changes associated with the LB surface as compared to cast film surfaces. The number of cells grown on the LB surface is greater than that on the cast film.

Synthesis and properties of new segmented block poly(urethane‐urea)s containing phosphatidylcholine analogues and polybutadienes

AbstractNew hydrophobic‐hydrophilic microphase‐separated block segmented copoly(urethane‐urea)s were synthesized by introducing hydrophobic polybutadienes as the soft segments and 4,4′‐methylenediphenyl diisocyanate, hexamethylene diisocyanate, ethylenediamine, and a hydrophilic phosphatidylcholine analogue as the hard segments in the backbones of these polymers. The results of ATR‐IR and XPS show the coexistence of phosphatidylcholine analogues and polybutadienes on the surface of cast films of the synthesized poly(urethane‐urea)s. Furthermore, TEM cross sectional observation of the cast film PBDP‐1370 indicates that it possesses a hydrophilic‐hydrophobic microphase‐separated domain structure.

Prevention of changes in platelet cytoplasmic free calcium levels by interaction with 2-hydroxyethyl methacrylate/styrene block copolymer surfaces.

Changes in platelet cytoplasmic free calcium levels were investigated in contact with cast film surfaces of a block copolymer containing 2-hydroxyethyl methacrylate (HEMA) and styrene (St) (0.5 mole fraction HEMA). These copolymer surfaces demonstrate microdomain alternating lamellae structures composed of hydrophilic HEMA domains (5 nm width) and hydrophobic St domains (20 nm width). The results were compared with those obtained from platelets contacting a random copolymer of HEMA-St (0.5 mole fraction HEMA) and from homopolymers of polystyrene (PSt) and poly(2-hydroxyethyl methacrylate) (PHEMA). Cytoplasmic free calcium levels in platelets contacting the microdomain structured surfaces of the HEMA-St block copolymer remained relatively constant in contrast to the significant increases observed for the radically prepared HEMA-St copolymer, PSt, and PHEMA surfaces. Adhering platelets were stimulated by exogenously introduced thrombin and calcium ionophore A23187 20 min after platelet adherence to the polymer surfaces. Only platelets on the block copolymer surfaces showed active metabolic responses. These results suggest that adhering platelets on the microdomain structured surfaces maintain high sensitivities to external stimulation due to an intrinsic strong inhibition of platelet functional changes induced by surface contact.

Cell adhesion onto block copolymer Langmuir-Blodgett films.

The attachment of cells onto the surfaces of various block copolymers fabricated either as well-defined, ordered Langmuir-Blodgett (LB) films, or solvent cast microphase-separated structures was studied. In general, more platelets adhered onto the multilayered LB surface than onto microphase-separated cast surfaces. Scanning electron micrographs of adhered platelets showed extensive morphological changes associated with the LB surface as compared to cast film surfaces. The morphology of adhered hepatocytes was similar for both LB films and cast surfaces. It may be assumed that the surface of a block copolymer LB film does not orient into microdomains, as in the solvent cast surfaces, and only one polymer domain interacts at the interface.

Ordered Structures of Styrene Butadiene Block Copolymers

Abstract Anionically prepared block copolymers of butadiene and styrene exhibit solution properties which result from a two dimensional ordering of the polymer molecules. The most notable of these properties is the iridescent colors of toluene solutions which are dependent on concentration and abruptly change on mechanical deformation. Electron micrographs of the surface of cast films indicate that the ordered structure is retained to some degree in the solid state.

Ordered structures of styrene–butadiene block copolymers

AbstractAnionically prepared block copolymers of butadiene and styrene exhibit solution properties which result from a two‐dimensional ordering of the polymer molecules. The most notable of these properties is the iridescent colors of toluene solutions which are dependent on concentration and abruptly change on mechanical deformation. Electron micrographs of the surface of cast films indicate that the ordered structure is retained to some degree in the solid state.