Preparation of a chemically amplified photosensitive polyimide based on norbornene‐end‐capped poly(amic acid ethoxymethylester)

A positive‐working chemically amplified photosensitive polyimide (PSPI) developable with basic aqueous solutions was obtained from poly(amic acid ethoxymethylester) (PAAE) as a polyimide precursor and diphenyliodonium 5‐hydroxynaphthalene‐1‐sulfonate (DINS) as a photoacid generator. The norbornene‐end‐capped PAAE based on 4,4′‐oxydiphthalic anhydride and 4,4′‐oxydianiline exhibited high transparency at 365 nm. The protection ratio of the ethoxymethyl groups was optimized to maximize the difference between the dissolution rates of the exposed and unexposed areas. The acid generated from DINS in the UV‐exposed region effectively deprotected the ethoxymethyl groups of PAAE by a chemical amplification mechanism. A 10‐μm‐thick film of the PSPI precursor system containing 16 wt % DINS exhibited a sensitivity (D^o) of 1100 mJ cm^?2 when developed with a 2.38 wt % aqueous tetramethyl ammonium hydroxide solution at room temperature. A fine, positive, 5‐μm line‐and‐space pattern was fabricated in a 15‐μm‐thick film with 1500 mJ cm^?2 of UV exposure. This resolution is excellent in comparison with those previously reported for chemically amplified PSPIs, and such a film can thus be used as a buffer coating in semiconductor packaging. © 2005 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 43: 5520–5528, 2005     

Relation between thermal conductivity and molecular alignment direction of free‐standing film aligned with rubbing method

The liquid crystal acryl compounds, in which the molecular directions were aligned by the rubbing method, were polymerized by UV irradiation, to provide the free‐standing aligned films of 200‐μm thickness. The relation between the thermal conductivity and the aligned molecular direction of the films was investigated. The homogeneous film showed the largest magnitude of the thermal conductivity at the direction along the molecular long axis (0.69 W/m K). This was 3.6 times greater than that of poly(methyl methacrylate). The thermal conductivity was dependent on the rotation angle and the concentration of the homogeneous molecular long axis fractions in the networks. These relations were investigated with the twisted film. © 2005 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 43: 3591–3599, 2005     

Synthesis of alkaline‐developable,photosensitive hyperbranched polyimides through the reaction of carboxylic acid dianhydrides and trisamines

Hyperbranched polyimides (HBPI)s with high glass‐transition temperatures and excellent thermal stability were synthesized through the reaction of commercially available carboxylic acid dianhydrides with tris[4‐(4‐aminophenoxy)phenyl]ethane (TAPE). In particular, hyperbranched polyimide HBPI(TAPE‐DSDA), prepared through the reaction of TAPE with 3,3′,4,4′‐diphenylsulfonetetracarboxylic dianhydride (DSDA), showed higher thermal stability and good solubility. Furthermore, alkaline‐developable, photosensitive HBPI(TAPE‐DSDA)‐MA‐CA was prepared through the reaction of HBPI(TAPE‐DSDA) with glycidyl methacrylate with tetrabutylammonium bromide as a catalyst in N‐methyl‐2‐pyrrolidinone (NMP) followed by the addition reaction of cis‐1,2,3,6‐tetrahydrophthalic anhydride with triphenylphosphine as a catalyst in NMP. The glass‐transition temperatures of HBPI(TAPE‐DSDA)‐MA‐CA were greater than 300 °C. A resist composed of 74 wt % HBPI(TAPE‐DSDA)‐MA‐CA, 22.2 wt % trimethylpropane triacrylate, and 3.8 wt % Irgacure 907 as a photoinitiator achieved a resolution of a 55‐μm line pattern and a 275‐μm space pattern by UV irradiation (1000 mJ/cm²). © 2004 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 42: 3697–3707, 2004     

Unusual inorganic phase formation in ultraviolet‐curable organic–inorganic hybrid films

Inorganic–organic hybrid materials were prepared with a cycloaliphatic epoxide adduct of linseed oil with tetraethylorthosilicate (TEOS) oligomers via a cationic UV‐curing process. The TEOS oligomers were prepared in the presence of water and ethanol with hydrochloric acid as a catalyst. The TEOS oligomers were characterized with ¹H and ²⁹Si NMR and matrix‐assisted laser desorption/ionization time‐of‐flight mass spectrometry. Hybrid films were cured, and the dynamic mechanical and thermal properties of the hybrid films were evaluated as a function of the TEOS oligomer content. The morphology of the hybrid films was examined with atomic force microscopy, transmission electron microscopy, and small‐angle light scattering. The microscopy and dynamic mechanical data indicated that the hybrid films were heterogeneous materials with various inorganic particle sizes dispersed within the organic matrix. In addition, ²⁹Si solid‐state NMR spectroscopy was used to investigate the coupling between the silicate region and organic regions. A schematic model is proposed to address structural features of hybrid materials. © 2005 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 43: 1607–1623, 2005     

Synthesis and positive‐imaging photosensitivity of soluble polyimides having pendant carboxyl groups

Polyimides having pendant carboxyl groups were prepared by a direct one‐pot polycondensation of 4,4′‐(hexafluoroisopropylidene)diphthalic anhydride (6FDA) with 3,5‐diaminobenzoic acid (DABz) and bis[4‐(3‐aminophenoxy)phenyl]sulfone (m‐BAPS) in the presence of a γ‐valerolactone/pyridine catalyst system using N‐methyl‐2‐pyrrolidone (NMP)/toluene mixture as a solvent at 180 °C. The obtained polyimides were soluble in dipolar aprotic solvents such as dimethylformamide, dimethyl sulfoxide, and NMP as well as in tetrahydrofuran and aqueous basic solution. The solubility of the polyimides was dependent on the diamine composition. Photosensitve polyimide (PSPI) systems composed of the polyimides and diazonaphthoquinone compound as a photosensitive material gave positive‐tone behavior by UV irradiation, followed by development with aqueous tetramethylammonium hydroxide (TMAH) solution. The scanning electron microscopic photograph of the resulting image showed 10‐μm line/space resolution with about 15 μm of film thickness. The PSPIs baked at 350 °C for a short time had excellent thermal resistance comparable to the original polyimides. © 2001 John Wiley & Sons, Inc. J Polym Sci A: Polym Chem 39: 934–946, 2001     

Grignard condensation routes to 1,3‐disilacyclobutane‐containing cyclolinear polycarbosilanes

Alkylene‐ and arylene‐bridged cyclolinear polycarbosilanes (CLPCS) with 1,3‐disilacyclobutane (DSCB) rings incorporated in the main chain of the polymer were prepared by polycondensation between corresponding di‐functional DSCB derivatives and di‐Grignard reagents. Well‐defined, low molecular weight (M_n = 3–5K; DP = 17–26), hexylene‐ and phenylene‐bridged CLPCS polymers were obtained without appreciable ring opening of the DSCB rings. Large exothermic peaks were observed in the DSC for these CLPCSs, which indicated, along with the IR spectra, that crosslinking occurred on heating to about 250 °C via the ring opening of the embedded, alternating, DSCB rings. Moreover, PB‐CLPCS undergoes photochemically induced crosslinking on UV irradiation to form crosslinked polycarbosilane network films. The spin‐cast, cured, films of these CLPCSs exhibit relatively low dielectric constants and promising thermal and mechanical properties for applications in electronics, for example, directly UV‐photoimprinted low‐k dielectrics. © 2017 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2017 , 55, 1547–1557     

Highly refractive polymer resin derived from sulfur‐containing aromatic acrylate

New sulfur‐containing polymers with high‐refractive indices and low birefringences have been developed as UV‐curable high‐refractive polymer resins. The polymers derived from 2,7‐bis[(2‐acryloylethyl)sulfanyl]thianthrene (2,7‐BAST) and 4,4′‐bis[(acryloyloxyethylthio)diphenylsulfide (4,4′‐BADS) were prepared by photopolymerization under UV irradiation. Transparent UV‐cured films were obtained in both cases. Both polymers showed good thermal stability, such as a 5% weight‐loss temperature at 355 °C under nitrogen and glass transition temperatures (T_g) in the range of 94–143 °C. They also showed high‐refractive indices of 1.6531 and 1.6645 at 632.8 nm and low birefringences of 0.0039 and 0.0069 in addition to high transparency in the visible region. © 2010 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 48: 2604–2609, 2010     

Synthesis of photosensitive and thermosetting poly(phenylene ether) based on poly[2,6‐di(3‐methyl‐2‐butenyl)phenol‐co‐2,6‐dimethyl‐phenol] and a photoacid generator

A chemically amplified photosensitive and thermosetting polymer based on poly[2,6‐di(3‐methyl‐2‐butenyl)phenol (15 mol %)‐co‐2,6‐dimethylphenol (85 mol %)] ( 3c ) and a photoacid generator [(5‐propylsulfonyloxyimino‐5H‐thiophen‐2‐ylidene)‐(2‐methylphenyl)acetonitrile] was developed. Poly[2,6‐bis(3‐methyl‐2‐butenyl)phenol]‐co‐2,6‐dimethylphenol)] ( 3 ) with high molecular weights (number‐average molecular weight ～ 24,000) was prepared by the oxidative coupling copolymerization of 2,6‐di(3‐methyl‐2‐butenyl)phenol with 2,6‐dimethylphenol in the presence of copper(I) chloride and pyridine as the catalyst under a stream of oxygen. The structures of 3 were characterized with IR, ¹H NMR, and ¹³C NMR spectroscopy. 3 was crosslinked by a thermal treatment at 300 °C for 1 h under N₂. The 5% weight loss temperatures and glass‐transition temperatures of the cured copolymers reached around 420 °C in nitrogen and 300 °C, respectively. The average refractive index of the cured copolymer ( 3c ) film was 1.5452, from which the dielectric constant at 1 MHz was estimated to be 2.6. The resist showed a sensitivity of 35 mJ cm^?2 and a contrast of 1.6 when it was exposed to 436‐nm light, postexposure‐baked at 145 °C for 5 min, and developed with toluene at 25 °C. A fine negative image featuring 8‐μm line‐and‐space patterns was obtained on a film exposed to 100 mJ cm^?2 with 436‐nm light in the contact‐printed mode. © 2004 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 43: 149–156, 2005     

Synthesis of an alkali‐swellable emulsion and its effect on the rate of polymer diffusion in poly(vinyl acetate‐butyl acrylate) latex films

We describe the synthesis and characterization of a weakly cross‐linked poly(methacrylic acid‐co‐ethyl acrylate) alkali‐swellable emulsion (ASE), as well as an investigation of its influence on the rate of polymer diffusion in latex films. The films examined were formed from poly(vinyl acetate‐co‐butyl acrylate) latex particles containing a small amount of acrylic acid as a comonomer. Polymer diffusion rates were monitored by the energy transfer technique. We found that the presence of the ASE component, either in the acid form or fully neutralized by ammonia or sodium hydroxide, had very little effect on the polymer diffusion rate. However, in the presence of 2 wt % NH₄‐ASE, there was a small but significant increase in the polymer diffusion rate. © 2005 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 43: 5632–5642, 2005     

Optical properties of the photorefractive polymeric composite with modified PVK polymer

Poly[N‐(2‐ethylhexyl)‐3‐vinylcarbazole has been synthesized by radical polymerization from N‐(2‐ethylhexyl)3‐vinyl‐carbazole. The 50‐μm thick photorefractive device containing 30 wt % piperidin‐4‐ylbenzylidene‐malononitrile showed a diffraction efficiency of 40% of 50 V/μm, which corresponded to a Δn of 0.8 × 10^?3. The photorefractive response time was τ₁ = 0.6 s. © 2009 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 47: 1695–1702, 2009     

Synthesis and characterization of ultraviolet‐curable hyperbranched poly(siloxysilane)s

Two UV‐curable hyperbranched poly(siloxysilane)s ( I and III ) containing vinyl and allyl end groups were synthesized via polyhydrosilylation with methylbis(methylethylvinylsiloxy)silane and methylbis(dimethylallylsiloxy)silane monomers. A cationic UV‐curable hyperbranched polymer ( II‐Ep ) with epoxy end groups was prepared via the hydrosilylation of hyperbranched polymer II with Si? H terminated groups and glycidyl methacrylate, and II was also obtained via the polyhydrosilylation of AB₂‐type monomer methylvinylbis(methylethylsiloxy)silane. All hydrosilylation reactions were catalyzed by Pt/C or chloroplatinic acid. Three AB₂‐type monomers were synthesized via the hydrolysis of functional chlorosilane, which was prepared with Grignard reagents and dichlorosilane. The molecular structures of the polymers were characterized with ¹H NMR, Fourier transform infrared, and gel permeation chromatography, and the UV‐curing behaviors of the polymers under different atmospheres and with different photoaccelerators were also investigated. The thermostability of uncured and cured polymers was examined with thermogravimetric analysis, and the data indicated that the orders of the onset decomposition temperatures for the cured polymers and the residue weights were as follows: III (380 °C) > I (320 °C) > II‐Ep (280 °C) and I (70.4%) > III (64.1%) > II‐Ep (60.9%), respectively. © 2005 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 43: 1883–1894, 2005     

A dismantlable photoadhesion system fabricated by an anionic UV curing of epoxy resins with a base amplifier having a disulfide bond

A base amplifier (BA) that autocatalytically generates a diamine having a disulfide bond has been developed. Diamines generated from this BA are integrated into cross‐linked networks of epoxy resins that also have disulfide bonds. Anionic UV curing is performed using a photobase generator, the BA and the epoxy resins, and cured films are obtained after UV irradiation and subsequent heating at 160 °C. Furthermore, this curing system is applied successfully to adhesion of two stainless substrates, which is cancelled with gentle heating and a shear force. © 2017 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2018 , 56, 237–241     

Photoreactive main‐chain liquid‐crystalline polyesters: Synthesis,characterization, and photochemistry

Three series of semiflexible and rigid main‐chain polyesters containing photoreactive mesogenic units derived from p‐phenylenediacrylic acid (PDA) and cinnamic acid have been synthesized by high‐temperature polycondensation. The thermal and mesomorphic properties of the polymers have been determined. The photochemical behavior of polymer P‐[1]‐T, which contains a PDA unit, has been studied both in solution and in films. In solution, [2+2] photocycloaddition, E/Z photoisomerization, and photo‐Fries rearrangement can take place. In contrast, the dominant process in spin‐coated films is the [2+2] photocycloaddition reaction, which causes crosslinking of the polymer. In films, the photochemistry and induction of anisotropy are strongly influenced by the aggregation of the PDA phenylester unit. A dichroism of about 0.2 has been induced in films by irradiation with linearly polarized UV light, and thus the capability of these films to induce optical anisotropy and align liquid crystals has been demonstrated. Liquid‐crystalline cells have been made with polarized irradiated films of P‐[1]‐T as aligning layers. A commercial liquid‐crystalline mixture has been used for this study, and a similar liquid‐crystalline order determined by polarized Fourier transform infrared to a commercial cell with rubbed polyimide as an aligning layer has been detected. Because of crosslinking of the irradiated P‐[1]‐T photoaligning layer, the photoinduced anisotropy is stable at high temperatures, and the liquid‐crystalline molecules are insoluble in the irradiated polymer. © 2005 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 43: 4907–4921, 2005     

Synthesis and healing properties of poly(arylene ether sulfone)‐poly(alkyl disulfide) multiblock copolymers

A multiblock copolymer consisting of hard (poly(arylene ether sulfone)) and soft (poly(alkyl disulfide)) segments was successfully synthesized by oxidative coupling of the corresponding thiol‐terminated oligomers. Its structure was confirmed by ¹H and ¹³C NMR spectroscopy. The GPC data (M_w = 82,000, M_w/M_n = 2.7) and inherent viscosity (0.67 dL g⁻¹) indicated the formation of a high‐molecular‐weight multiblock copolymer, while AFM and DSC indicated a microphase‐separated morphology. Tensile testing of the multiblock copolymer films showed a large elongation at break, which is characteristic of microphase‐separated hard/soft multiblock copolymers. Over 90% of the elongation at break of damaged samples (notched or cut) was recovered by UV irradiation. The elongation recovery was proportional to the UV irradiation energy, and the high recovery was achieved by relatively weak irradiation (<170 J cm⁻²). The high content of disulfide bonds in the multiblock copolymer resulted in a lower self‐healing energy. © 2018 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2018 , 56, 1358–1365     

Preparation of siloxane‐based urethane dimethacrylates carrying carboxylic groups and the effect of silver nanoparticles on the properties of composite polymer films

This work reports on the synthesis of three acid oligosiloxane‐urethane dimethacrylates and their use to obtain hybrid nanocomposite films, in which the presynthesized silver nanoparticles (NPs) were incorporated before photopolymerization, or produced via in situ photoreduction of the silver nitrate (AgNO₃) precursor into the formulation, without any conventional reducing agent. All samples were characterized by ¹H NMR, FT‐infrared and UV spectroscopies, photodifferential scanning calorimetry (photo‐DSC), transmission electron microscopy (TEM), and energy‐dispersive X‐ray (EDX) analysis. Fourier transformed infrared spectroscopy and photo‐DSC results showed that dimethacrylates having hydrophilic segment of poly(ethylene oxide) type in structure are more reactive than the acid oligosiloxane dimethacrylate. When another urethane dimethacrylate is taken as a comonomer, the photopolymerization rate (0.112–0.132 s^?1) and the degree of conversion (82–93%) significantly increased. Experimental evidence of the existence of nanosilver into the polymer matrix generated upon UV irradiation has been supported by UV spectroscopy, EDX and TEM analysis, the last allowing a visualization of the formation of silver NPs with size between 2 and 15 nm. Mechanical parameters and wettability of the photocrosslinked films are also discussed in the prospect of further potential applications in the biomedical field. © 2011 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem, 2012     

Two‐sided comb poly(amic ester)–poly(propylene oxide) graft copolymers as porous polyimide precursors

New step‐growth graft block copolymers were synthesized. These two‐sided comb copolymers consisted of a poly(amic ester) (PAE) backbone and pendant poly(propylene oxide) (PPO) grafts. The copolymers were made via a macromonomer approach, in which the 4,6‐bischlorocarbonyl isophthalic acid bis[poly(propylene oxide)] ester macromonomer was synthesized through the reaction of hydroxyl‐terminated PPO oligomers with pyromellitic dianhydride and oxalyl chloride. This macromonomer was subsequently used in step‐growth polymerization with comonomers 4,6‐bischlorocarbonyl isophthalic acid diethyl ester, 2,5‐bischlorocarbonyl terephthalic acid diethyl ester, and 2,2‐bis[4‐ (4‐aminophenoxy)phenyl] hexafluoropropane, and this yielded PPO‐co‐PAE graft copolymers. Accordingly, we report the synthesis and characterization of the PPO oligomer, the PPO macromonomer, and their corresponding PPO‐co‐PAE graft copolymers. Graft copolymers with PPO concentrations of 3–26 wt % were synthesized. These polymers were thermally cured to produce polyimide/PPO composites. The thermolysis of these polyimide/PPO composites yielded porous polyimide films with porosities ranging of 4–22.5%. © 2005 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 43: 2266–2275, 2005     

Syntheses of conductive adhesives based on epoxy resin and polyanilines by using N‐tert‐butyl‐5‐methylisoxazolium perchlorate as a thermally latent curing reagent

Conductive composites consisted of epoxy resin and polyanilines (PANIs) doped with dodecylbenzenesulfonic acid ( 1 ), dodecylsulfonic acid (2), di(2‐ethylhexyl)sulfosuccinic acid (3), and HCl were synthesized by use of N‐tert‐butyl‐5‐methylisoxazolium perchlorate (5) under various reaction conditions. It was found that the composites with PANI doped with acid 2 (PANI‐2) prepared by curing with 10 mol % of reagent 5 at 80 °C for 12 h showed high electroconductivity along with the low conducting percolation threshold (3 wt % of PANI‐2). Furthermore, the composite with even ?10 wt % of PANI‐2 exhibited ?10^?1 S/cm of electroconductivity. The UV–vis and IR measurements indicated that the conductive emeraldine salt form of PANI‐2 in the composite was maintained after the curing reaction. The thermal stability was studied by TGA and DSC measurements, and then, the T_d10 and T_g of the composite with 5 and 10 wt % of PANI‐2 were found to be similar to those with the cured epoxy resin itself. In addition, the similar investigation with an oxetane resin instead of the epoxy resin was also carried out. © 2005 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 44: 718–726, 2006     

Fabrication of novel conjugated polymer nanostructure: Porphyrins and fullerenes conjugately linked to the polyacetylene backbone as pendant groups

A new series of conjugated polyacetylenes with conjugately linked fullerene and porphyrin groups as pendant units were prepared by a copolymerization reaction catalyzed by chloronorbornadiene rhodium(I)dimer‐triethylamine ([Rh(nbd)Cl]₂‐NEt₃) in anhydrous CHCl₃. These polymers were characterized with UV–vis spectroscopy, fluorescence spectroscopy, and voltammetry. Scanning electron microscopy indicated that the morphology of the copolymers consisted of uniform nanorods with a diameter of about 100 nm and a length of about 300 nm. Thin films of the copolymers produced steady and prompt photocurrent at an irradiation of 20.0 mW cm^?2 of white light, which was higher than that of a mixture of poly[5‐(4‐Ethynyl‐phenyl)‐10,15,20‐tris(4‐carbomethoxyphenyl)porphyrin zinc] and C₆₀. © 2005 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 43: 2851–2861, 2005     

Synthesis and chiroptical properties of optically active polymer liquid crystals containing azobenzene chromophores

A series of optically active methacrylic homopolymers, poly[(4‐{4′‐[(S)‐2‐methyl‐1‐butyloxycarbonyl]phenylazo}phenoxyl)x‐methylene methacrylate] (x = 0, 2, 6, or 11), were synthesized. The structures of the polymers were characterized by IR, ¹H NMR, UV, differential scanning calorimetry, and gel permeation chromatography. The chiroptical properties of the polymers in films were investigated with circular dichroism (CD) measurements. The CD and UV spectra of the films suggested that CD absorptions occurred in the films of the polymers with long spacers (x = 6 or 11) but not in the films of the polymers with short spacers (x = 0 or 2). After irradiation with linearly polarized light at 442 nm, the CD values were amplified in all the polymeric films. The amplificatory values of the CD bands in the absorption region (260–360 nm) of azobenzene chromophores suggested that the spacer length had an effect on both the transfer of chirality and photoinduced chirality in the polymeric films. The largest level of photoinduced chirality was induced in the polymer containing six methylene units. © 2006 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 44: 3210–3219, 2006     

Synthesis and nonlinear optical properties of side chain liquid crystalline polymers containing azobenzene push–pull chromophores

Azobenzene monomeric precursors bearing piperazine as donor moiety with different withdrawing groups and derived side chain polymethacrylates have been prepared and characterized. Monomers having terminal cyano or nitro groups, and the corresponding polymers, exhibited smectic A phases. Linear and nonlinear optical properties of every monomer and thin films of the cyano polymer ( pol‐PZ‐CN ) have been also studied. UV‐vis spectroscopy revealed out‐of‐plane orientation in the as prepared films, as confirmed by waveguide refractive index measurements. Moreover, absorption spectra indicated the presence of azo aggregates in these films. The initial molecular arrangement has been modified by applying thermal annealing within the mesophase range and UV‐blue irradiation. Although thermal annealing resulted in a significant amplification of the out‐of‐plane optical anisotropy due to thermotropic self‐organization of side chain azo moieties, irradiation with 440 nm light induced some disruption of aggregates. The nonlinear optical response of Corona poled films has been studied by second harmonic generation measurements, and the influence of the molecular arrangement on the nonlinear d_ij coefficients has been analyzed. The more efficient poling corresponded to preirradiated films. In any case, a noticeable degree of polar order (70% of the initial d₃₃ value) remained for several months after the poling in films kept at RT. © 2009 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 48: 232–242, 2010