Preparation and photopatterning of Langmuir–Blodgett (LB) films of a novel copolymer containing swallow‐tailed double naphthalene groups

A new series of copolymer poly(N‐hexadecylmethacrylamide‐co‐dinaphthalen‐2‐yl 2‐allylmalonate) poly(HDMA‐co‐DNAM)s containing swallow‐tailed double naphthyl groups and long alkyl group were designed and synthesized. The behavior of copolymer molecular arranging on water surface, patterning properties of copolymer LB films, and photochemical reactions in ultrathin film were investigated. The poly(HDMA‐co‐DNAM)s could form a stable, well‐defined molecular orientation Langmuir monolayer at air/water interface. The polymer main chain was lying flat on water surface and the side chains attached to the main chain stretching out at the angle of about 50°. The results obtained showed that a well‐ordered layer‐by‐layer structure was successfully controlled in LB films, in which most of naphthyl groups in poly(HDMA‐co‐DNAM)s LB films were in dimer and the copolymer LB films were decomposed hardly upon irradiation of deep UV light. We found that the exposed and unexposed regions of the poly(HDMA‐co‐DNAM)s copolymer LB films had solubility differentiation in gold etchant, which is a mixed solution of I₂/NH₄I/C₂H₅OH/H₂O. Therefore, we could obtain gold photopattern with the maximal resolution of the employed mask without any development process. Copyright © 2011 John Wiley & Sons, Ltd.     

Development of 1‐Hydroxy‐2(1H)‐quinolone‐Based Photoacid Generators and Photoresponsive Polymer Surfaces

A new class of carboxylate and sulfonate esters of 1‐hydroxy‐2(1H)‐quinolone has been demonstrated as nonionic photoacid generators (PAGs). Irradiation of carboxylates and sulfonates of 1‐hydroxy‐2(1H)‐quinolone by UV light (λ≥310 nm) resulted in homolysis of weak N? O bond leading to efficient generation of carboxylic and sulfonic acids, respectively. The mechanism for the homolytic N? O bond cleavage was supported by time‐dependent DFT calculations. Photoresponsive 1‐(p‐styrenesulfonyloxy)‐2‐quinolone–methyl methacrylate (SSQL‐MMA) and 1‐(p‐styrenesulfonyloxy)‐2‐quinolone–lauryl acrylate (SSQL‐LA) copolymers were synthesized from PAG monomer 1‐(p‐styrenesulfonyloxy)‐2‐quinolone, and subsequently controlled surface wettability was demonstrated for the above‐mentioned photoresponsive polymers.     

Self‐Aligned Micropatterns of Bifunctional Polymer Surfaces with Independent Chemical and Topographical Contrast

Bifunctional surfaces are micropatterned using a self‐aligned, dual‐purpose lithographic mask and pairs of conformally deposited iCVD polymers. A first layer is deposited, then physically masked and etched in oxygen plasma. A second layer is deposited with the mask still in place. Lift‐off reveals the micropatterned surface. The thicknesses of the two layers are independently controlled so that the resultant surface displays both chemical and topographical contrast. The patterning scheme is independent of the polymers used and order of deposition. We use this scheme to create surfaces that spatially confine microcondensation, as well as chemical functionality. We also demonstrate microwells whose depth can be altered in response to a water stimulus.

     

Synthesis and characterization of novel liquid‐crystalline copolymers containing thermally stable photochromic groups

To overcome the defects of the thermal instability of azobenzene, a series of novel photochromic, chiral, liquid‐crystalline monomers and polymers were synthesized from (+)‐camphor. The copolymerization of the photochromic monomers with comonomers was carried out. The synthesized monomers and polymers were identified with nuclear magnetic resonance, Fourier transform infrared, and elemental analysis. The composition of the copolymers was estimated with elemental analysis. The specific rotation of the chiral compounds and polymers was evaluated. The thermal stability and phases of the polymers during heating and cooling cycles were studied with differential scanning calorimetry and thermogravimetric analysis. The phases of the polymers were identified with polarized optical microscopy textures and X‐ray diffraction analysis. The distance between the layers of smectic liquid crystals was estimated from the diffraction angles. Photoisomerization of the configurational E/Z structures was investigated with an ultraviolet–visible spectrophotometer with 300‐nm ultraviolet irradiation. The thermal stability of the Z‐structural segment in the polymers was confirmed through the heating of the polymer at 70 °C for over 10 h. The photoisomerization and thermal stability of the C?C bond in the polymeric materials were demonstrated through a series of novel chiral polymers synthesized in this investigation. Both the polarity of the center part and the molecular length at the ends of the molecules were found to be necessary factors for the formation of liquid‐crystalline molecules. © 2007 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 45: 2026–2037, 2007     

UV‐induced refractive index modulation of photoreactive polymers bearing N‐acylcarbazole groups

In this study, we report on the synthesis and characterization of photoreactive polymers bearing N‐acetylcarbazole and N‐formylcarbazole groups, respectively. These polymers were easily accessible by polymer analogous acylation of commercially available poly‐(2‐vinylcarbazole). While poly(1‐(2‐vinyl‐9H‐carbazol‐9‐yl)ethanone) (poly‐ 1 ) undergoes a partial photochemical Fries rearrangement, poly(2‐vinyl‐9H‐carbazole‐9‐carbaldehyde) (poly‐ 2 ) decarbonylates smoothly when exposed to UV irradiation. The difference in reactivity between the two acylated polymers is because of the lower stability of the formyl radical, which is formed in the first stage of this photoreaction. Ellipsometric measurements of thin films showed that the photo‐Fries rearrangement in poly‐ 1 causes a change in refractive index by Δn = +0.01 at 650 nm. UV illumination of poly‐ 2 results in a change of the refractive index by Δn = +0.03 at 650 nm, which can be explained by the high yield of the photodecarbonylation of the N‐formylcarbazole groups. Refractive index patterns can be easily realized using lithographic techniques as demonstrated by optical microscopy using a phase contrast set‐up for visualization. Patterned films of poly‐ 1 and poly‐ 2 with feature sizes of about 5 μm were obtained with a mask aligner. Photoreactive polymers bearing N‐acylcarbazole groups are of potential interest for optical applications such as waveguides, optical switches, and data storage devices. © 2010 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem, 2010     

Photo‐crosslinked fluorinated thin films from azido‐functionalized random copolymers

Random copolymers of styrene, p‐azidomethylstyrene and 1H,1H,2H,2H‐perfluorodecyl methacrylate were prepared in two steps involving nitroxide‐mediated radical copolymerization and azidation reaction and further characterized by ¹H and ¹⁹F NMR, size exclusion chromatography, differential scanning calorimetry, and thermal gravimetric analysis. Ultrathin films of these azidomethyl‐functionalized fluorinated random copolymers, with thicknesses ranging from 20 to 100 nm, were spin coated onto Si substrates and then crosslinked by ultraviolet irradiation resulting in smooth and insoluble crosslinked fluorinated polymer mats. The surface properties of the supported thin films were investigated by X‐ray photoelectron spectroscopy and water contact angle measurements. These tailored photo‐crosslinked coatings afford a versatile control and homogenization of the wetting properties of different organic and inorganic substrates. © 2010 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 48: 3888–3895, 2010     

Behaviors of self‐assembled diblock copolymer with pendant photosensitive azobenzene segments

A novel monomer, ethyl 4‐[4‐(11‐methacryloyloxyundecyloxy)phenyl azobenzoyl‐oxyl] benzoate, containing a photoisomerizable N?N group was synthesized. The monomer was further diblock copolymerized with methyl methacrylate. Amphiphilic diblock copolymer poly(methyl methacrylate‐block‐ethyl 4‐[4‐(11‐methacryloyloxyundecyloxy)phenyl azobenzoyl‐oxyl] benzoate ( PMMA ‐ b ‐ PAzoMA ) was synthesized using atom transfer radical polymerization. The reverse micelles with spherical construction were obtained with 2 wt % of the diblock copolymer in a THF/H₂O mixture of 1:2. Under alternating UV and visible light illumination, reversible changes in micellar structure between sphere and rod‐like particles took place as a result of the reversible E‐Z photoisomerization of azobenzene segments in PMMA ‐ b ‐ PAzoMA . Microphase separation of the amphiphilic diblock copolymer in thin films was achieved through thermal and solvent aligning methods. The microphases of the annealed thin films were investigated using atom force microscopy topology and scanning electron microscopy analyses. © 2010 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 48: 1142–1148, 2010     

Synthesis and properties of methacrylate‐based networked polymers having ionic liquid structures

Methacrylate‐based networked polymers having ionic liquid structures were prepared by radical copolymerization of methyl methacrylate (MMA) with multifunctional crosslinkers: ethyleneglycol dimethacrylate (EGDMA), trimethylolpropane trimethacrylate (TMPTMA), or triethyleneglycol dimethacrylate (TEGDMA), in the presence of 1‐ethyl‐3‐methylethyl‐1‐imidazolium bis(trifluoromethane)sulfonyl imide (EMImTFSI). The fundamental physical properties of several film samples prepared by varying the monomer composition and ionic liquid content were investigated. The obtained materials became turbid with increasing crosslinker content and ionic liquid content. Their ionic conductivity increased with increasing ionic liquid content, while it was almost independent of the crosslinker content. EGDMA‐derived materials and TMPTMA‐derived materials showed higher ionic conductivity than TEGDMA‐derived materials. TMPTMA‐derived materials showed higher thermal stability than EGDMA or TEGDMA‐derived materials. EGDMA and TMPTMA‐derived materials were stiffer than the TEGDMA‐derived materials. The elastic modulus of the film samples increased but the film became more brittle with the increase of crosslinker content. Scanning electron microscopy and atomic force microscopy observation revealed that phase separation of networked polymers and ionic liquid occurred in the highly crosslinked samples, and the phase separation structures became larger in scale with the increase of crosslinking density. This phase separation was considered to have a strong effect on the mechanical properties of the film samples. © 2010 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem, 2010     

Synthesis of polyesters with pendant oxetane groups by the chemoselective alternating copolymerization of 3‐ethyl‐3‐(glycidyloxymethyl)oxetane with carboxylic anhydride and its photochemical reaction

The synthesis of polyesters with pendant oxetane groups by the chemoselective alternating copolymerization of 3‐ethyl‐3‐(glycidyloxymethyl)oxetane (EGMO) with carboxylic anhydride and the photochemical reaction of the resulting polymer was examined. The alternating copolymerization of EGMO with phthalic anhydride proceeded chemoselectively with quaternary onium salts under appropriate reaction conditions, and the corresponding soluble polymers with pendant oxetane groups with number‐average molecular weights of 4700–7200 were obtained in 72–87% yields. Furthermore, the photochemical reaction of the resulting polymers was examined with certain photoacid generators in the film state upon UV irradiation, and it was found that the photocrosslinking reaction of the pendant oxetane groups proceeded smoothly to give the insoluble polymers. © 2003 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 41: 1952–1961, 2003     

Synthesis and morphology investigations of a novel alkyne‐functionalized diblock copolymer

We reported the synthesis and morphology of a novel alkyne‐functionalized diblock copolymer (di‐BCP) poly(methyl methacrylate‐random‐propargyl methacrylate)‐block‐poly(4‐bromostyrene). The di‐BCPs were synthesized by atom transfer radical polymerization and postpolymerization deprotection, with good control over molecular weight and polydispersity index. Microphase separation in bulk di‐BCPs was confirmed by thermal analysis, small‐angle X‐ray scattering, and transmission electron microscopy. Microphase‐separated morphologies were also observed in thin films, and the orientation of the microdomains can be conveniently controlled by annealing under different solvents. © 2012 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys, 2012     

Synthesis and characterization of low‐bandgap copolymers based on dihexyl‐2h‐benzimidazole and cyclopentadithiophene

A series of new semiconducting polymers based on 4,4‐dihexyl‐4H‐cyclopenta[2,1‐b:3,4‐b′]dithiophene, 2,2‐dihexyl‐2H‐benzimidazole, and thiophene units was synthesized. The polymers show good solubility at room temperature in organic solvents owing to long alkyl chain in new acceptor, 2,2‐dihexyl‐2H‐benzimidazole. The advantage of dihexyl‐2H‐benzimidazole compared to the benzothiadiazole is to improve the solubility of the polymer. It was found that these polymers can finely be tuned for photovoltaic application by adjusting the contents ratio of the dihexyl‐2H‐benzimidazole unit. The spectra of the solid films show absorption bands with maximum peaks in the range of 421–577 nm and the absorption onsets at 588–683 nm, corresponding to band gaps of 2.11–1.82 eV. The devices with PCPDTDTHBI‐1 :PC₇₁BM showed an open‐circuit voltage (V_OC) of 0.46 V, a short‐circuit current density (J_SC) of 3.83 mA/cm², and a fill factor of 0.36, giving a power conversion efficiency of 0.64%. Decrease of the dihexyl‐2H‐benzimidazole contents in the polymers induced red‐shift of the UV absorptions, and increased V_OC and J_SC values, to improve the efficiency of organic photovoltaics. © 2010 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem, 2010     

Block copolymer films on patterned surfaces

We present results from a numerical study of a coarse-grained model of diblock copolymer (BCP) thin films cast on a chemically patterned surface. The patterned surface contains chemical inhomogeneities with a repeat spacing length scale comparable to the linear size of the BCP molecules. We find that the orientation of the lamellae in the thin film and the overlap of the film morphology with the preassigned surface pattern is strongly influenced by the commensurability between the bulk unconstrained lamellar size λ^*, and the linear size of the surface inhomogeneities w. PACS Numbers: 64.60.Cn, 61.41.+e, 64.60.My, 64.75.+g. © 1998 John Wiley & Sons, Inc. J Polym Sci B: Polym Phys 36: 3127–3136, 1998     

Controllable photopatterning and photochemical properties of novel copolymer containing dianthracene langmuir–blodgett films

A new series of copolymer poly(N‐hexadecylmeth acrylamide‐co‐bis(anthracen‐9‐ylmethyl) 2‐allylmalonate) [poly(HDMA‐co‐DAnMAMA)]s containing swallow‐tailed double anthracenyl groups and long alkyl group are designed and synthesized. The main route of the photochemical reaction of the p(HDMA‐DAnMAMA)copolymer Langmuir–Blodgett (LB) films is dimerization reaction between the anthracenyl groups under the irradiation of both 365 and 248 nm for limiting irradiation time, resulting to a fine negative‐tone pattern. On the other hand, the anthracenyl groups act just as photodecomposition group under 248 nm for longer irradiation time, resulting to a fine positive‐tone pattern. Consequently, positive‐tone and negative‐tone pattern are obtained by choosing not only a suitable irradiation light wavelength, but the irradiation time at 248 nm. Moreover, it is found that the exposed and unexposed regions of copolymer LB films irradiated at 248 nm have solubility differentiation in gold etchant (I₂/NH₄I/C₂H₅OH/H₂O), that is to say, the gold photopatterns with the maximal resolution of the used mask can be obtained easily without any development process. © 2011 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 50: 139–147, 2012     

Relevance of linked dye‐coinitiator in visible three‐component photoinitiating systems: Application to red light photopolymerization

A new visible light photoinitiating system (PIS) containing a linked dye‐coinitiator dyad and a nondissociative electron donor was evaluated and compared with unlinked three components systems. Our results show that in the physical mixture of the three component PIS, addition of the nondissociative donor decreased the Rp to a great extent, whereas in combination with the dyads an increase in Rp is observed. The results were explained based on faster intramolecular electron transfer in linked pairs and point out the importance of linked initiator in three‐component PIS for the first time. This system is the first example of three‐components system with a nondissociative donor that would be useful for long life coating formulation. © 2013 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2013, 51, 4325–4330     

Segmental dynamics in poly(ε‐caprolactone)/poly(L‐lactide) copolymer networks

Poly(ε‐caprolactone) (PCL) and poly(lactic acid) (PLA) networks were prepared from macromonomer diols functionalized with methacrylic anhydride, which allows one to get self‐crosslinkable polymers. Besides, both macromonomers were copolymerized to get copolymer networks with different compositions (namely, PCL/PLA: 0/100, 70/30, 50/50, 30/70, 100/0). Dielectric and calorimetric experiments allow one to conclude the microphase separation of the system: one phase made of pure PCL domains while the second one consists of caprolactone units, which somehow plasticize PLA and moves its main relaxation (glass transition) to lower temperatures. The effect of crosslinking PLA on the dynamics of the system was further investigated by comparing with the dynamics for linear PLA. © 2008 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 47: 183–193, 2009     

Sequence‐Dependent Photocurrent Generation through Long‐Distance Excess‐Electron Transfer in DNA

Given its well‐ordered continuous π stacking of nucleobases, DNA has been considered as a biomaterial for charge transfer in biosensors. For cathodic photocurrent generation resulting from hole transfer in DNA, sensitivity to DNA structure and base‐pair stacking has been confirmed. However, such information has not been provided for anodic photocurrent generation resulting from excess‐electron transfer in DNA. In the present study, we measured the anodic photocurrent of a DNA‐modified Au electrode. Our results demonstrate long‐distance excess‐electron transfer in DNA, which is dominated by a hopping mechanism, and the photocurrent generation is sequence dependent.     

Versatile preparation of poly(1,4‐phenylenevinylene‐co‐1,4‐phenylene‐1,2‐ethanediyl) by CVD polymerization of p‐(methoxymethyl)benzyl chloride

It was demonstrated that a series of copolymers consisting of 1,4‐phenylenevinylene (PV) and 1,4‐phenylene‐1,2‐ethanediyl (PE) units could be prepared from a single monomer, p‐(methoxymethyl)benzyl chloride, via the chemical vapor deposition polymerization (CVDP) method. The composition of the copolymers could be varied simply by altering the monomer activation temperature. The higher the temperature, the lower the content of the PV unit. The photo (PL)‐ and electroluminescence (EL) properties of the copolymers that revealed a blueshift when compared with PPV strongly depend on the amount of the PE units incorporated. The external quantum efficiencies of the electroluminescence devices having the configuration of ITO/PEDOT‐PSS/copolymer/Al‐Li were higher than that of PPV, which can be ascribed to the improved confinement of excitons. © 2005 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 43: 742–751, 2005     

Synthesis and photophysical properties of Rhodamine B dye‐bearing poly(isobutyl methacrylate‐co‐2,2,2‐trifluoroethyl methacrylate) as a temperature‐sensing polymer film

To develop a novel temperature‐sensitive paint, methacrylamide monomers bearing Rhodamine B dye (two regioisomers, 3a and 3b ) were synthesized and polymerized with isobutyl methacrylate and 2,2,2‐trifluoroethyl methacrylate to afford Rhodamine B‐pendant polymers 4a and 4b . The methacrylamide monomers 3a and 3b showed photophysical properties almost identical with those of Rhodamine B. The temperature sensitivity of the luminescence intensity of 3a and 3b was also similar to that of Rhodamine B. The polymers 4a and 4b have excellent solubility in nonpolar organic solvents and are suitable for application as paint. Films of polymers 4a and 4b showed temperature‐dependent luminescence, which is applicable for temperature‐sensing. The temperature sensitivity of the film of 4a was estimated to be ?0.37% °C^?1, and was independent of pressure. The film of 4b showed higher temperature sensitivity, but its temperature sensitivity was slightly pressure‐dependent. Hence, polymer 4a is expected to be superior for practical use in paints having temperature‐sensing functionality. © 2007 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 45: 2876–2885, 2007     

Initiated Chemical Vapor Deposition and Light‐Responsive Cross‐Linking of Poly(vinyl cinnamate) Thin Films

The first vapor‐phase deposition of poly(vinyl cinnamate) (PVCin) is reported. Initiated chemical vapor deposition (iCVD) is used to synthesize PVCin thin films with an average thickness of 100 nm. Free radical polymerization and cyclization reactions compete during the deposition process, with approximately 45% of the repeat units undergoing cyclization. Exposure to UV light (λ = 254 nm) induces dimerization (cross‐linking) of the PVCin, which is quantified using spectroscopic techniques. Approximately 90% of the free cinnamate moieties are dimerized at a UV dose of 300 mJ cm⁻². PVCin is also incorporated into a copolymer with N‐isopropylacrylamide, which exhibits a characteristic change in hydrophilicity with temperature. The copolymer is selectively cross‐linked through a mask, and reversible swelling of patterns with 30 μm resolution is demonstrated by submerging the film in water.