Molecular parameters and their relation to the adhesive performance of emulsion acrylic pressure‐sensitive adhesives. II. Effect of crosslinking

Acrylic emulsion pressure‐sensitive adhesive (PSA) films generally have much lower shear holding power than that of their solvent‐borne counterparts for the same peel and tack. This is due to their discrete microgel morphology in the film. In contrast, film cast from solution‐polymerized acrylic PSA forms a continuous network as a result of crosslinking acrylic acid and aluminum acetyl acetonate (AAA) in the film following the solvent evaporation. Novel acrylic emulsion PSA was made by copolymerizing ≤1 wt % isobutoxy methyl acrylamide (IBMA) in the polymer backbone. The IBMA grafted the linear portion of the acrylic polymer with the microgels upon heating the film, which resulted in a significant increase in the shear holding power. © 2001 John Wiley & Sons, Inc. J Appl Polym Sci 79: 2558–2564, 2001     

Molecular parameters and their relation to the adhesive performance of acrylic pressure‐sensitive adhesives

Model acrylic pressure‐sensitive adhesives (PSAs) based on poly(2‐ethyl‐hexyl acrylate‐stat‐acrylic acid) and poly(n‐butyl acrylate‐stat‐acrylic acid) at 97.5/2.5 wt % were synthesized using semicontinuous emulsion and solution polymerizations. Microgels formed in the lattices retained their discrete network morphology in the film. In contrast, acrylic solution was essentially gel free and crosslinking in the film was provided by the reaction of acrylic acid and post added Al Acetyl Acetonate after solvent evaporation, which led to continuous network morphology. The difference in film network morphology caused significantly lower shear holding power for the film from emulsion PSA compared with that of solvent‐borne film. Unlike shear holding power, loop tack and peel of acrylic PSAs were mainly controlled by the same sol/gel molecular parameters, regardless of emulsion or solution PSAs. The important molecular parameters are sol‐to‐gel ratio, entanglement molecular weight, weight average molecular weight, and to a lesser extent, glass transition temperature. © 2001 John Wiley & Sons, Inc. J Appl Polym Sci 79: 2230–2244, 2001     

Effect of natural polyphenols on physicochemical properties of crosslinked gelatin‐based polymeric biocomposite

This work was aimed to study the effect of natural polyphenols extract (Acacia nilotica bark) on physicochemical properties of crosslinked gelatin‐poly(acrylamide‐co‐acrylic acid), Gel‐poly(AAm‐co‐Ac), polymeric biocomposite film. Gelatin‐based composite films have extensive application as biocompatible biomaterial as drug carriers, cosmetics, and agricultural food packaging. The prepared composite films were characterized using Fourier transform infrared spectroscopy (FTIR) and differential scanning calorimetry (DSC), in addition to the swelling and degradation behavior. UV‐Vis absorption spectra and scanning electron microscopy (SEM) were also applied to observe the interaction between Gel‐poly(AAm‐co‐Ac) and natural polyphenol (catechin). The study has demonstrated that the involvement of hydrogen bonding and hydrophobic interactions as the major forces involved in the stabilization of gelatin‐based polymeric biocomposite film by the plant polyphenols (catechin and gallic acid derivatives). Thermal stability studies of crosslinked gelatin‐based composite film revealed that A. nilotica bark extract stabilizes the gelatin molecules and leads to moderate increase of the denaturation temperatures relative to the uncrosslinked one. © 2010 Wiley Periodicals, Inc. J Appl Polym Sci, 2010     

Effect of trifunctional cross-linker triallyl isocyanurate (TAIC) on the surface morphology and viscoelasticity of the acrylic emulsion pressure-sensitive adhesives

Acrylic pressure sensitive adhesive (PSA) latexes were synthesized via a starved monomer-seeded semi-continuous emulsion polymerization process with butyl acrylate (BA), methyl methacrylate, acrylic acid (AA), 2-hydroxyethyl acrylate and trifunctional cross-linker, triallyl isocyanurate (TAIC). Influences of TAIC on the resultant latex and PSA properties were comprehensively investigated. The results indicated that latex particle size was independent of the amount of TAIC in the pre-emulsion feed, while the viscosity of the latex increased remarkably with TAIC content increased. Thermal gravimetric analysis result showed that the thermal stability of the polymers was improved significantly with the addition of TAIC. Besides, with the increase in TAIC content, gel content of the polymer increased significantly, while molecular weight between cross link points (M_c) and sol molecular weight (M_w, M_n) of the polymer decreased remarkably. Moreover, for the cross-linked adhesive film, the shear strength was improved greatly while at the sacrifice of loop tack and peel strength, when compared with the uncrosslinked counterparts. Finally, dynamic mechanical analysis and atomic force microscopy were also used to evaluate the viscoelastic properties and surface morphology of the acrylic emulsion PSA film, respectively.     

Preparation and performance of a transparent poly(3,4‐ethylene dioxythiophene)–poly(p‐styrene sulfonate‐co‐acrylic acid sodium) film with a high stability and water resistance

Poly(p‐styrene sulfonate‐co‐acrylic acid sodium) (PSA) from the copolymerization of acrylic acid sodium and p‐styrene sulfonate monomers were used to dope poly(3,4‐ethylene dioxythiophene) (PEDOT) to generate PEDOT–PSA antistatic dispersions. Compared to those of the PEDOT–poly(p‐styrene sulfonate sodium) (PSS), the physical and electrical properties of the PEDOT–PSA conductive liquids were much better. The PEDOT–PSA films possessed a better water resistance without a decrease in the conductivity. The sheet resistance of the PEDOT–PSA–poly(ethylene terephthalate) (PET) films was about 1.5 × 10⁴ Ω/sq with a 100 nm thickness, the same as the PEDOT–PSS–PET films. The transmittance of the PEDOT–PSA–PET films exceeded 88%. Furthermore, the environmental dispersity of the PEDOT–PSA antistatic dispersion was apparently improved by the dopant PSA so that the stability was extraordinarily promoted. Meanwhile, the water resistances of the PEDOT–PSA–PET and PEDOT–PSA films were also enhanced. © 2017 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2017 , 134, 45163.     

Hydrogenated rosin ester latexes/waterborne polyacrylate blends for pressure‐sensitive adhesives

Diethylene glycol ester of hydrogenated rosin (DGE‐HR) emulsion was prepared via phase inversion method and then blended with waterborne (wb) polyacrylate for pressure‐sensitive adhesives (PSAs). The preparation conditions of DGE‐HR emulsion were studied. DGE‐HR emulsion with an average particle size of about 220 nm was obtained. Furthermore, the thermal, adhesive, and viscoelastic properties and the morphology of DGE‐HR/polyacrylate composite were investigated. Thermal analysis indicated that glass transition temperatures (T_g) of the DGE‐HR/polyacrylate blends became higher as the DGE‐HR content increased and DGE‐HR did not have a significant influence on thermal stability of the blend films. Atomic Force Microscopy (AFM) observation revealed that the DGE‐HR particles added had a good miscibility with acrylic particles. Additionally, for these tackified acrylic PSAs, positive correlations between mechanical performance and viscoelastic response at bonding and debonding frequencies were also found. © 2015 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2016 , 133, 42965.     

Aging of Model Pressure Sensitive Adhesives Studied with Scanning Probe Microscopy

Changes in the surface morphology and surface friction of a tackified model pressure sensitive adhesive (PSA) with aging have been observed directly with atomic force microscopy. Changes over many months at room temperature as well as changes during brief exposure to two elevated temperatures (65 and 100°C) were characterized. Performance of the PSA, consisting of poly(ethylene propylene) with n-butyl ester of abietic acid as the tackifier, was studied qualitatively with nanoindentation.

Tackifier-enriched domains at the blends' surfaces grew and then coalesced with aging and the surface friction decreased as a result. Also, the polymer-enriched matrix stiffened with time. These two effects led to a stiffer surface, poorly suited to wetting an adherend. Domain coalescence was markedly accelerated upon brief exposure to a temperature ramp up to 100°C. At the highest temperatures studied, degradation of the polymeric matrix decreased its stiffness.     

Miscibility and pressure‐sensitive adhesive performances of acrylic copolymer and hydrogenated rosin systems

Relationship between the miscibility of pressure‐sensitive adhesives (PSAs) acrylic copolymer/hydrogenated rosin systems and their performance (180° peel strength, probe tack, and holding power), which was measured over a wide range of time and temperature, were investigated. The miscible range of the blend system tended to become smaller as the molecular weight of the tackifier increased. In the case of miscible blend systems, the viscoelastic properties (such as the storage modulus and the loss modulus) shifted toward higher temperature or toward lower frequency and, at the same time, the pressure‐sensitive adhesive performance shifted toward the lower rate side as the T_g of the blend increased. In the case of acrylic copolymer/hydrogenated rosin acid systems, a somewhat unusual trend was observed in the relationship among the phase diagram, T_g, and the pressure‐sensitive adhesive performance. T_g of the blend was higher than that expected from T_gs of the pure components. This trend can be due to the presence of free carboxyl group in the tackifier resin. However, the phase diagram depended on the molecular weight of the tackifier. The pressure‐sensitive adhesive performance depended on the viscoelastic properties of the bulk phase. A few systems where a single T_g could be measured, despite the fact that two phases were observed microscopically, were found. The curve of the probe tack of this system shifted toward a lower rate side as the T_g increases. However, both the curve of the peel strength and the holding power of such system did not shift along the rate axis. © 1999 John Wiley & Sons, Inc. J Appl Polym Sci 71: 651–663, 1999     

Hydroxyethyl chitosan‐g‐poly(acrylic acid‐co‐sodium acrylate) superabsorbent polymers

A novel hydroxyethyl chitosan‐g‐poly(acrylic acid‐co‐Sodium Acrylate) (HECTS‐g‐(PAA‐co‐PSA)) superabsorbent polymer was prepared through graft copolymerization of acrylic acid and sodium acrylate onto the chain of hydroxyethyl chitosan. The structure of the polymer was characterized by FTIR. By studying the water absorption of the polymer synthesized under different conditions, the optimal conditions for synthesizing the polymer with the highest swelling ratio was defined. This superabsorbent polymer was further treated by the solvent precipitation method and by the freeze‐drying method. We found that the water absorption rate of the treated polymer was greatly increased and the microstructure of the treated polymer was changed from small pores to loose macro pores. The swelling processes of the polymers before and after modification fit first‐order dynamic processes. The amount of the residual acrylic acid was greatly decreased after treatments. © 2010 Wiley Periodicals, Inc. J Appl Polym Sci, 2010     

Surface modification of linear low‐density polyethylene film by amphiphilic graft copolymers based on poly(higher α‐olefin)‐graft‐poly(ethylene glycol)

In this article, a series of amphiphilic graft copolymers, namely poly(higher α‐olefin‐co‐para‐methylstyrene)‐graft‐poly(ethylene glycol), and poly(higher α‐olefin‐co‐acrylic acid)‐graft‐poly(ethylene glycol) was used as modifying agent to increase the wettability of the surface of linear low‐density polyethylene (LLDPE) film. The wettability of the surface of LLDPE film could be increased effectively by spin coating of the amphiphilic graft copolymers onto the surface of LLDPE film. The higher the content of poly(ethylene glycol) (PEG) segments, the lower the water contact angle was. The water contact angle of modified LLDPE films was reduced as low as 25°. However, the adhesion between the amphiphilic graft copolymer and LLDPE film was poor. To solve this problem, the modified LLDPE films coated by the amphiphilic graft copolymers were annealed at 110° for 12 h. During the period of annealing, heating made polymer chain move and rearrange quickly. When the film was cooled down, the alkyl group of higher α‐olefin units and LLDPE began to entangle and crystallize. Driven by crystallization, the PEG segments rearranged and enriched in the interface between the amphiphilic graft copolymer and air. By this surface modification method, the amphiphilic graft copolymer was fixed on the surface of LLDPE film. And the water contact angle was further reduced as low as 14.8°. The experimental results of this article demonstrate the potential pathway to provide an effective and durable anti‐fog LLDPE film. © 2010 Wiley Periodicals, Inc. J Appl Polym Sci, 2011     

Miscibility and fracture energy of probe tack for acrylic pressure-sensitive adhesives: acrylic copolymer/tackifier resin systems

The relationship between the miscibility of acrylic pressure-sensitive adhesive (PSA) and the fracture energy (W) (Jm⁻²) of the probe tack was investigated, wherein the master curve of W was compared with that of the maximum force (σ_max) (gf) of the probe tack. It was ascertained that W of acrylic PSA was closely related to the miscibility between the components (acrylic copolymer and tackifier resin). In the case of the miscible blend system, the master curve of W shifted toward the lower rate side and, at the same time, the magnitude decreased as the tackifier resin content increased. The degree of the shift of W was extremely smaller than that of σ_max. In the case of the immiscible blend system, the master curve of W remarkably decreased as the tackifier resin content increased, which suggests the fact that W of the PSA depended on the dynamic mechanical properties of the matrix phase and that the resin-rich phase acted as a kind of filler, thus reducing the practical performance. © 1998 John Wiley & Sons, Inc. J Appl Polym Sci 69: 581–587, 1998     

Preparation and properties of poly[styrene‐co‐(butyl acrylate)‐co‐(acrylic acid)]/silica nanocomposite latex prepared using an acidic silica sol

BACKGROUND: Polyacrylate/silica nanocomposite latexes have been fabricated using blending methods with silica nanopowder, in situ polymerization with surface‐functionalized silica nanoparticles or sol–gel processes with silica precursors. But these approaches have the disadvantages of limited silica load, poor emulsion stability or poor film‐forming ability. RESULTS: In this work, poly[styrene‐co‐(butyl acrylate)‐co‐(acrylic acid)] [P(St‐BA‐AA)]/silica nanocomposite latexes and their dried films were prepared by adding an acidic silica sol to the emulsion polymerization stage. Morphological and rheological characterization shows that the silica nanoparticles are not encapsulated within polymer latex particles, but interact partially with polymer latex particles via hydrogen bonds between the silanol groups and the ? COOH groups at the surface of the polymer particles. The dried nanocomposite films have a better UV‐blocking ability than the pure polymer film, and retain their transparency even with a silica content up to 9.1 wt%. More interestingly, the hardness of the nanocomposite films increases markedly with increasing silica content, and the toughness of the films is not reduced at silica contents up to 33.3 wt%. An unexpected improvement of the solvent resistance of the nanocomposite films is also observed. CONCLUSION: Highly stable P(St‐BA‐AA)/silica nanocomposite latexes can be prepared with a wide range of silica content using an acidic silica sol. The dried nanocomposite films of these latexes exhibit simultaneous improvement of hardness and toughness even at high silica load, and enhanced solvent resistance, presumably resulting from hydrogen bond interactions between polymer chains and silica particles as well as silica aggregate/particle networks. Copyright © 2009 Society of Chemical Industry     

Morphology and structure changes of aromatic copolysulfonamide fibers heat‐drawn at various temperatures

Pre‐drawn aromatic copolysulfonamide (co‐PSA) fibers were prepared by wet spinning and then heat drawing at temperatures varying from 350 to 390 °C, which are below the decomposition temperature. The fibers were then characterized using tensile testing, dynamic mechanical analysis, wide‐angle X‐ray diffraction and small‐angle X‐ray scattering. The relationship between structure and properties of the co‐PSA fibers drawn at different temperatures was investigated. The heat‐drawn co‐PSA fibers displayed similar glass transition temperature of about 355 °C, which was higher than that of pre‐drawn co‐PSA fibers of 345 °C. The crystal orientation was high as a crystalline structure formed during heat drawing and the crystallinity increased with the heat‐drawing temperature. However, the tenacity of the co‐PSA fibers did not increase linearly with the draw temperature. When the drawing temperature was higher than the glass transition temperature, a decrease in tenacity was observed, which could be attributed to an increase of crystallite size of the (100) plane and a decrease of the long period of the lamellar structure. © 2014 Society of Chemical Industry     

Synthesis of acrylate polymers by a novel emulsion polymerization for adhesive applications

Pressure‐sensitive adhesives (PSAs) are viscoelastic–elastomeric materials that can adhere strongly to solid surfaces with light contact pressure and a short contact time. Polyacrylates produced by solution polymerization are used widely because of their good adhesive properties. A novel emulsion polymerization was established to improve the low physical properties of PSA on the basis of conventional poly(n‐butyl acrylate) (PBA) by emulsion polymerization. PBA latex was synthesized by the emulsion polymerization of 50 wt % n‐butyl acrylate mixed with 15 wt % ethyl acetate (EA) with Emal‐10P and Emulgen‐920 as anionic and nonionic surfactants, respectively, at 70°C. Potassium persulfate (KPS) or a combination of KPS and dicumyl peroxide (DCP) was used as the initiator. The KPS/DCP system gave a very high‐molecular‐weight PBA of a narrow molecular weight distribution with a weight‐average molecular weight/number‐average molecular weight value of 1.01–1.03 in 15 min. The PSA tape was prepared by the casting of the PSA latex onto a corona poly(ethylene terephthalate) film as an adherent to obtain a 50‐μm‐dry‐thickness film. The PSA tape produced from PBA by the novel emulsion polymerization showed better adhesive properties, such as 180° peel adhesion, shear holding power, and rolling ball tack tests according to JIS and ASTM standards, than PSA tape produced from solution polymerization. The occlusion of a small amount of EA in emulsion particles before polymerization was found to give higher properties than those of PBA prepared by the addition of EA to the PBA latex after polymerization. © 2006 Wiley Periodicals, Inc. J Appl Polym Sci 100:413–421, 2006     

Thermal properties of proton-conducting radiation-grafted membranes

Proton-exchange membranes are required to exhibit chemical, mechanical, and thermal stability for fuel cell applications. The present investigation has been carried out to explore the thermal behavior of poly(ethylene-alt-tetrafluoroethylene) (ETFE)-based proton-conducting membranes, both uncrosslinked and crosslinked, prepared by radiation grafting and subsequent sulfonation. The influence of preparation steps (irradiation, grafting, sulfonation, crosslinking) on the thermal degradation, crystallinity, and melting behavior of membranes with varying degree of grafting was examined. ETFE base film and grafted films were studied as the reference materials. Furthermore, poly(tetrafluoroethylene-co-hexafluoropropylene)-based grafted films and membranes were investigated as well for comparison. Membrane preparation steps, degree of grafting, crosslinking, type of base polymer have considerable influence on the thermal properties of membranes. The crystallinity of the films decreases slightly by grafting, while a significant decrease was observed after sulfonation. For instance, crystallinity decreased from 37% (pristine ETFE) to 36% (uncrosslinked grafted film) and 23% (uncrosslinked ETFE-based membrane). On the other hand, the melting temperature of the base polymer was almost unaffected by irradiation and grafting. The crosslinked ETFE-based membranes exhibit a slightly higher melting temperature (262.5°C) than their corresponding grafted films (261.3°C) and the base film (260.6°C). © 2008 Wiley Periodicals, Inc. J Appl Polym Sci, 2008     

Chitosan and N‐carboxymethylchitosan: I. The role of N‐carboxymethylation of chitosan in the thermal stability and dynamic mechanical properties of its films

Chitosan (degree of deacetylation of 90.2%) and N‐carboxymethylchitosan (N‐CMCh) (degree of substitution of 18.5%) were analyzed using thermogravimetric analysis in order to determine their thermal stability. Also, their films were evaluated using scanning electron microscopy (SEM) and mechanical and dynamic mechanical analysis (DMA). Both polymers showed a thermal degradation peak at T_m ～ 250 °C, with T_onset and weight loss of 175 °C and 62% and 190 °C and 35% for chitosan and N‐CMCh, respectively. N‐CMCh showed a second thermal degradation peak at T_m = 600 °C, with an additional weight loss of 25%. Kinetic thermal analysis showed a slower process of degradation at 100 °C for N‐CMCh compared with chitosan, and an activation energy 13 times higher for the former, confirming the higher stability of N‐CMCh. Analysis of chitosan and N‐CMCh films showed that the latter support a high tension, with lower elasticity, and, as revealed by DMA, N‐CMCh has a more compact film structure, with a crossing arrangement of N‐CMCh fibers, as compared with the chitosan films which were determined from SEM analysis to have fibers in one direction only. Copyright © 2006 Society of Chemical Industry     

Mechanical properties of latex blends films from polystyrene particles with different sizes in a butyl acrylate‐co‐styrene copolymer matrix

Blends of polystyrene (PSt) hard particle latex with three different particle sizes (96, 72, and 61 nm) and a n‐butyl acrylate‐co‐styrene (BA‐co‐St) copolymer soft latex with a 204 nm particle size were synthesized by emulsion polymerization. Latexes were standardized at 25% solids and blended at different concentrations by wt% of PSt:BA‐co‐St for every hard particle size. Finally, films from each blend were obtained. Morphology of each film prepared was examined by transmission electron microscopy, and it was found that the hard particles are randomly distributed in the films inside the copolymer matrix. The effect on mechanical properties of different PSt concentrations and particle sizes was assessed by DMA as a function of temperature. The results indicate that rigidity of the blended latex increases as the particle size diminishes as determined by the reduction in damping in the tan δ peak. The storage modulus increases as the concentration of PSt increases in the blends and the values depend upon the size of PSt particles. Mechanical properties at tension indicate that decreasing the size of the PSt particles and increasing their concentration increase the Young's modulus and ultimate strength at tension because of an increase in the rigidity of the films. POLYM. ENG. SCI., 2009. © 2009 Society of Plastics Engineers     

Preparation and physical properties of LLDPE grafted with novel nonionic surfactants

Copolymers of linear low‐density polyethylene (LLDPE) grafted with two novel nonionic surfactants, acrylic glycerol monostearate ester (AGMS) and acrylic polyoxyethylenesorbitan monooleate ester (ATWEEN80), containing hydrophilic and hydrophobic groups and 1‐olefin double bond were prepared by using a plasticorder at 190°C. To evaluate the grafting degree, two different approaches based on ¹H‐NMR data were proposed, and FTIR calibration was showed to validate these methods. The rheological response of the molten polymers, determined under dynamic shear flow at small‐amplitude oscillations, indicated that crosslinking formation of the chains could be decreased with increasing the monomer concentration. Their thermal behavior was studied by DSC and polarization microscope (PLM): The crystallization temperature (T_C) of grafted LLDPE shifted to higher temperature compared with neat LLDPE because the grafted chains acted as nucleating agents. Water and glycerol were used to calculate the surface free energy of grafted LLDPE films. The results indicated that the novel polyoxyethylene surfactant ATWEEN80 could greatly improve the hydrophilicity of LLDPE and the surface free energy varied from 33 mN/m of neat LLDPE to 106 mN/m of the grafted LLDPE film. © 2008 Wiley Periodicals, Inc. J Appl Polym Sci, 2009     

Preparation of narrow‐disperse or monodisperse poly{[poly(ethylene glycol) methyl ether acrylate]‐co‐(acrylic acid)} microspheres with ethyleneglycol dimethacrylate as crosslinker by distillation precipitation polymerization

Narrow‐disperse or monodisperse poly{[poly(ethylene glycol) methyl ether acrylate]‐co‐(acrylic acid)} (poly(PEGMA‐co‐AA)) microspheres were prepared by distillation precipitation polymerization with ethyleneglycol dimethacrylate (EGDMA) as crosslinker with 2,2′‐azobisisobutyronitrile as initiator in neat acetonitrile in the absence of any stabilizer, without stirring. The diameters of the resultant poly(PEGMA‐co‐AA‐co‐EGDMA) microspheres were in the range 200–700 nm with a polydispersity index of 1.01–1.14, which depended on the comonomer feed of the polymerization. The addition of the hydrogen bonding monomer acrylic acid played an essential role in the formation of narrow‐disperse or monodisperse polymer microspheres during the polymerization. Copyright © 2006 Society of Chemical Industry     

Preparation and characterization of photoreactive copolymers containing curable pendants for positive photoresist

tert‐Butyl methacrylate (TBMA) was copolymerized with various comonomers that were selected from methyl methacrylate (MMA), n‐butyl acrylate (NBA), acrylic acid (AA), and 2‐hydroxyethyl methacrylate (HEMA). From film physical properties, poly(TBMA‐co‐HEMA) and poly(TBMA‐co‐AA‐co‐NBA), were selected as resin binders. To introduce unsaturated double bonds onto the side chain of copolymers, they were further functionalized with acryloyl chloride and glycidyl methacrylate. Copolymers synthesized in this investigation were all identified by using FTIR and NMR. The thermal decomposition temperature of functionalized poly(TBMA‐co‐HEMA) showed obvious difference before and after crosslinking. Adding a small amount of EGDMA as the crosslinking agent could increase the degree of crosslinking and obviously improve the physical properties. Functionalized poly(TBMA‐co‐HEMA) was used as a binder resin and composed with a photoacid generator for positive photoresists. From exposure characteristics, the optimal lithographic condition was achieved when exposed for 90 s, PEB at 100°C for 2.5 min, and developed in 10 wt % Na₂CO₃ developer for 30 s. After completing the lithography process, the residual pattern of positive photoresist was further treated at 140°C for 30 min to cure the pendant unsaturated groups. The resolution of the positive photoresist was analyzed by an optical microscope and SEM technique. © 2001 John Wiley & Sons, Inc. J Appl Polym Sci 80: 328–333, 2001