UV‐photodimerization in uracil‐substituted dendrimers for high density data storage

Two series of uracil‐functionalized dendritic macromolecules based on poly (amidoamine) PAMAM and 2,2‐bis(hydroxymethylpropionic acid) bis‐MPA backbones were prepared and their photoinduced (2π+2π) cycloaddition reactions upon exposure to UV light at 257 nm examined. Dendrimers up to 4th generation were synthesized and investigated as potential materials for high capacity optical data storage with their dimerization efficiency compared to uracil as a reference compound. This allows the impact of increasing the generation number of the dendrimers, both the number of chromophores, as well as the different steric environments, on the performance of each series of dendrimers to be investigated. The (uracil)₁₂‐[G‐2]‐bis‐MPA and (uracil)₈‐[G‐1]‐PAMAM were observed to have high dimerization efficiency in solution with different behavior being observed for the PAMAM and bis‐MPA dendrimers. The dendrimers with the best dimerization efficiency in solution were then examined in the solid state as thin films cast on quartz plates, and their film qualities along with their photodimerization performance studied. High quality films with a transmission response of up to 70% in 55 s. when irradiated at 257 nm with an intensity of 70 mW/cm² could be obtained suggesting future use as recording media for optical data storage. © 2007 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 45: 4401–4412, 2007     

Synthesis,characterization, photo‐induced alignment,and surface orientation of poly(9,9‐dioctylfluorene‐alt‐azobenzene)s

Three types of bi‐functionalized copolymers ( P1FAz , P2FAz , and P3FAz ) with different numbers of fluorene units and an azobenzene unit were synthesized and characterized using UV–vis and polarized absorption spectroanalysis. The trans‐cis photoisomerization was conformed under 400 nm light irradiation for all copolymers in chloroform. However, in the film state, only the trans‐cis photoisomerization occurred by mono‐fluorene attached copolymer poly[(9,9‐di‐n‐octylfluorenyl‐2,7‐diyl)‐alt‐4,4′‐azobenzene)] ( P1FAz ). Photo‐induced alignment was achieved using the P1FAz film after irradiation with linear polarized 400 nm light and subsequent annealing at 60 °C. Surface orientation of a spin‐coating film of poly(9,9‐didodecylfluorene) ( F12 ) was achieved using the photo‐induced alignment layer of the P1FAz film after annealing at 90 °C. The photo‐induced alignment layer of P1FAz has potential application to the surface orientation technique for appropriate polymers, which will be useful for the fabrication of optoelectronics devices. © 2012 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem, 2012     

Synthesis and Characterization of PEG‐Based Drug‐Responsive Biohybrid Hydrogels

Interactive materials being responsive to a biocompatible stimulus represent a promising approach for future therapeutic applications. In this study, we present a novel biohybrid material synthesized from biocompatible components being stimulus‐responsive to the pharmaceutically approved small‐molecule novobiocin. The hydrogel design is based on the gyrase B (GyrB) protein, which is covalently grafted to multi‐arm polyethylene glycol (PEG) using a Michael‐type addition reaction. Upon addition of the GyrB‐dimerizing substance coumermycin, stable hydrogels form which can be dissolved in a dose‐adjustable manner by the antibiotic novobiocin. The switchable properties of this PEG‐based hydrogel are favorable for future applications in tissue engineering and as externally controlled drug depot.     

Preparation of novel photoreactive polycarbazole‐based microparticles: Reactivity features

Four types of innovative benzophenone (BPh)‐ or aryl azide (ArAz)‐containing photoreactive polycarbazole (polyCbz)‐based microparticles (MPs) were prepared using an oxidative liquid phase polymerization system. Their photochemical reactivity was evaluated by their reaction with highly inert poly(2‐chloro‐paraxylelene) (Parylene C) films. Possible mechanisms for the photochemical reaction of those MPs with Parylene C were discussed. The highly photoreactive BPh was found to react more inside the particle causing internal cross‐linking of MP polyCbz chains, fusion between adjoining particles and deformation of their spherical structure. In contrast, the less reactive but more selective ArAz‐containing MPs were found to react much more with Parylene C. The strong reactivity of such photoreactive MPs toward Parylene C films emphasizes a general method for the functionalization of stable nonfunctional polymeric coatings. This paves the way to simple and solvent‐free functionalization of nonfunctional coatings and materials by light. © 2011 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem, 2011     

Asymmetric leakage in (Ba,Sr)TiO3 nanoparticle/parylene‐C composite capacitors

Nanoparticle polymer composite capacitors have been examined for some time as a route to high performance, printable capacitors. One approach to creating these composites is to use a particle film together with vapor deposited polymers, which can yield high performance, but also forms a structurally asymmetric device. The performance of a nanoparticle (Ba, Sr)TiO₃ (BST)/parylene‐C composite capacitor is compared to that of a nanoparticle BST capacitor without the polymer layer under both directions of bias. The composite device shows a five orders of magnitude improvement in the leakage current under positive bias of the bottom electrode relative to the pure‐particle device, and four orders of magnitude improvement when the top electrode is positively biased. The voltage tolerance of the device is also improved and asymmetric (44 V vs. 28 V in bottom and top positive bias, respectively). This study demonstrates the advantage of this class of composite device construction, but also shows that proper application of the device bias in this type of asymmetrical system can yield an additional benefit. © 2012 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys, 2013     

Synthesis of novel dithienothiophene‐ and 2,7‐carbazole‐based conjugated polymers and H‐bonded effects on electrochromic and photovoltaic properties

Three kinds of dithienothiophene/carbazole‐based conjugated polymers ( P1–P3 ), which bear acid‐protected and benzoic acid pendants in P2 and P3 , respectively, were synthesized via Suzuki coupling reaction. Interestingly, P1 – P3 exhibited reversible electrochromism during the oxidation processes of cyclic voltammogram studies, and P3 (with H‐bonds) revealed the best electrochromic property with the most noticeable color change. According to powder X‐ray diffraction (XRD) analysis, these polymers exhibited obvious diffraction features indicating bilayered packings between polymer backbones and π‐π stacking between layers in the solid state. Compared with the XRD data of P2 (without H‐bands), H‐bonds of P3 induced a higher crystallinity in the small‐angle region (corresponding to a higher ordered bilayered packings between polymer backbones), but with a similar crystallinity in the wide angle region indicating a comparable π‐π stacking distance between layers. Moreover, based on the preliminary photovoltaic properties of PSC devices ( P1 – P3 blended individually with PCBM acceptor in the weight ratio of 1:1), P3 (with H‐bonds) possessed the highest power conversion efficiency of 0.61% (with J_sc = 2.26 mA/cm², FF = 29.8%, and V_oc = 0.9 V). In contrast to P2 (without H‐bands), the thermal stability, crystallinity, and electrochromic along with photovoltaic properties of P3 were generally enhanced due to its H‐bonded effects. © 2012 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem, 2012     

Comparative study of 2‐amino and 3‐aminobenzoic acid copolymerization with aniline synthesis and copolymer properties

Polyanilines soluble in an aqueous basic medium were synthesised by copolymerization of aniline (ANI) with both 2 and 3‐aminobenzoic acids (ABA). Different composition copolymers were prepared by varying the ANI/ABA feed ratio. Poly(aniline‐co‐2‐aminobenzoic acid) (PANI2ABA) and poly(aniline‐co‐3‐aminobenzoic acid) (PANI3ABA) displayed differences in their properties, such as specific charge and fluorescence behavior because the reactivity of 2‐aminobenzoic (2ABA) and 3‐aminobenzoic (3ABA) acids are very different. The new materials were characterized by X‐ray photoelectron, Fourier transform infrared, and Raman spectroscopies. © 2004 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 42: 5587–5599, 2004     

Synthesis of polymeric 1‐iminopyridinium ylides as photoreactive polymers

Two synthetic routes to polymeric 1‐imino pyridinium ylides as new photoreactive polymeric architectures were investigated. In the first approach, polymerization of newly synthesized 1‐imino pyridinium ylide containing monomers yielding their polymeric analogues was achieved by free radical polymerization. Alternatively, reactive precursor polymers were synthesized and converted into the respective 1‐imino pyridinium ylide polymers by polymer analogous reactions on reactive precursor polymers. Quantitative conversion of the reactive groups was achieved with pentafluorophenyl ester containing polymers and newly synthesized photoreactive amines as well as by the reaction of poly(4‐vinylbenzoyl azide) with a photoreactive alcohol. The polymers obtained by both routes were examined regarding their photoreaction products and kinetics in solution as well as in thin polymer films. Contact angle measurements of water on the polymer films before and after irradiation showed dramatic changes in the hydrophilicity of the polymers. © 2010 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 48: 832–844, 2010     

High Tg,ambipolar, and near‐infrared electrochromic anthraquinone‐based aramids with intervalence charge‐transfer behavior

Two novel series of ambipolar and near‐infrared electrochromic aromatic polyamides with electroactive anthraquinone group were synthesized from new aromatic diamines, 2‐(bis(4‐aminophenyl)amino)anthracene‐9,10‐dione and 2‐(4‐(bis(4‐aminophenyl)amino)phenoxy)anthracene‐9,10‐dione, respectively, via low‐temperature solution polycondensation reaction. These polymers were readily soluble in many polar solvents and showed useful levels of thermal stability associated with high glass‐transition temperatures (T_g) (285–360 °C). Electrochemical studies of these electrochromic polyamides revealed ambipolar behavior with reversible redox couples and high contrast ratio both in the visible range and near‐infrared region. © 2011 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem, 2012     

Hypervalent iodine‐mediated direct azidation of polystyrene and consecutive click‐type functionalization

Polystyrene was directly azidated in 1,2‐dichloroethane or chlorobenzene using a combination of trimethylsilyl azide and a hypervalent iodine (III) compound, (diacetoxyiodo)benzene. 2D NMR HMBC experiments indicated that the azide groups were attached to the polymer backbone and also possibly to the aromatic pendant groups. The amount of introduced azide groups was estimated by semi‐quantitative IR spectroscopy and elemental analysis. Approximately 1 in every 11 styrene units could be modified by using a ratio of hypervalent iodine compound to trimethylsilyl azide to styrene units of 1:2.1:1 at 0 °C for 4 h followed by heating to 50 °C for 2 h in chlorobenzene. The azidated polymers were further used as backbone precursors in the synthesis of polymeric brushes with hydrophilic side chains via a copper‐catalyzed click grafting‐onto reaction with poly(ethylene oxide) monomethyl ether 4‐pentynoate. © 2010 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 48: 966–974, 2010     

Synthesis of polymers possessing tetraphenylethylene units by three‐component coupling reactions of poly(p‐phenylene ethynylene) derivative with aryl halides and phenylboronic acid

A derivative of poly(p‐phenylene ethynylene) was subjected to the palladium‐catalyzed three‐component coupling reactions with aryl halides and phenylboronic acid to obtain polymers having tetrasubstituted cis‐vinylene units. For example, 69% of the acetylene units in the prepolymer were converted to cis‐vinylene (i.e., tetrasubstituted cis‐vinylene) units using iodobenzene and phenylboronic acid (5 equiv each with respect to acetylene units). In the UV–vis absorption spectra of the resulting polymers, clear hypsochromic shifts of the absorption maxima were observed, while bathochromic shifts and suppression of the efficiency were observed in their photoluminescence spectra. © 2015 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2015 , 53, 787–791     

Glycoconjugated polymer: Synthesis and characterization of poly(vinyl saccharide)‐block‐polystyrene‐block‐poly(vinyl saccharide) as an amphiphilic ABA triblock copolymer

Styrene (St) was polymerized with α,α′‐bis(2′,2′,6′,6′‐tetramethyl‐1′‐piperidinyloxy)‐1,4‐diethylbenzene ( 1 ) as an initiator (bulk, [St]/] 1 ] = 570) at 120 °C for 5.0 h to obtain polystyrene having 2,2,6,6‐tetramethylpiperidiloxy moieties on both sides of the chain ends ( 2 ) with a number‐average molecular weight (M_n) of 14,300 and a polydispersity index [weight‐average molecular weight/number‐average molecular weight (M_w/M_n)] of 1.14. 4‐Vinylbenzyl glucoside peracetate ( 3a ) was polymerized with 2 as a macromolecular initiator and dicumyl peroxide (DCP) as an accelerator in chlorobenzene at 120 °C. The polymerization with the [ 3a ]/[ 2 ]/[DCP] ratio of 30/1/1.2 for 5 h afforded a product in a yield of 73%; it was followed by purification with preparative size exclusion chromatography to provide the ABA triblock copolymer containing the pendant acetyl glucose on both sides of the chain ends ( 4a ; M_n = 21,000, M_w/M_n = 1.16). Similarly, the polymerization of 4‐vinylbenzyl maltohexaoside peracetate produced the ABA triblock copolymer containing the pendant acetyl maltohexaose on both side of the chain end ( 4b ; M_n = 31,800, M_w/M_n = 1.11). Polymers 4a and 4b were modified by deacetylation into amphiphilic ABA triblock copolymers containing the pendant glucose and maltohexaose as hydrophilic segment, 5a and 5b , respectively. © 2006 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 44: 3978–3985, 2006     

New hyperbranched second‐order nonlinear optical poly(arylene‐ethynylene)s containing pentafluoroaromatic rings as isolation group: Facile synthesis and enhanced optical nonlinearity through Ar‐ArF self‐assembly effect

In this article, a facile route was designed to prepare four new hyperbranched poly(arylene‐ethynylene)s containing azo‐chromophore moieties through one‐pot “A₂+B₃” approach via simple Sonogashira coupling reaction. The polymers were all soluble in organic solvents and demonstrated good nonlinear optical (NLO) properties, because of the three‐dimensional spatial isolation effect of these hyperbranched polymers. Due to the different B₃‐type comonomer, the self‐assembly effect of pentafluoroaromatic in the interior of these polymers were different, leading to the different trends of the NLO activities. © 2012 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem, 2012     

Synthesis of Polyethylene Containing Allene Groups: A Simple and Efficient Route to Functional Polyethylene

Allene groups are first employed as the reactive moiety in the simple and efficient synthesis of well‐defined functional polyethylene. By copolymerization of ethylene with allene group substituted norbornene, the allene group is successfully introduced into the polyethylene with a high content. The retained allene groups are demonstrated to be highly reactive in following photoinduced functionalized reactions and can be efficiently converted into the functional groups without the multi‐step, time consuming processes that have generally been required in previous reports, providing the side group‐functionalized polyethylene with a wide range of functional group content.     

Blue‐light‐emitting and anodically electrochromic materials of new wholly aromatic polyamides derived from the high‐efficiency chromophore 4,4′‐dicarboxy‐4″‐methyltriphenylamine

A series of organosoluble, aromatic polyamides were synthesized from a 4‐methyl‐substituted, triphenylamine‐containing, aromatic diacid monomer, 4,4′‐dicarboxy‐4″‐methyltriphenylamine, which is a blue‐light (454‐nm) emitter with a fluorescence quantum efficiency of 46%. These triphenylamine‐based, high‐performance polymers had strong fluorescence emissions in the blue region with high quantum yields up to 64% and one reversible oxidation redox couple around 1.20 V versus Ag/AgCl in acetonitrile solutions. They exhibited good thermal stability, with 10% weight loss temperatures above 480 °C under a nitrogen atmosphere and with relatively high glass‐transition temperatures (252–309 °C). All the polyamides revealed excellent stability of electrochromic characteristics, changing color from the original pale yellow to blue. © 2006 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 44: 4095–4107, 2006     

Functionalizable biodegradable photocrosslinked elastomers based on 2‐oxepane‐1,5‐dione

The use of aliphatic polyesters for biomedical applications is limited by the lack of functionality of their backbones. The aim of the following study was to develop a novel elastic scaffold material containing functional groups to be used for future derivatization to tether peptide ligands to support cell adhesion, migration, and differentiation. The elastomer was based on three‐arm star copolymers composed of ε‐caprolactone and a functionalized ε‐caprolactone, 2‐oxepane‐1,5‐dione, and end‐terminated with acrylate groups. The elastomer thus contains a ketone and two approaches were examined for obtaining a photocrosslinkable elastomer containing functional groups: crosslinking followed by ketone reduction using sodium borohydride to generate pendant hydroxyl groups, and reaction of the ketone with hydrazines. Reduction of the ketone lead to degradation of the elastomer through transesterification and ethanolate mediated cleavage of the polymer backbone. Reaction with hydrazines did not degrade the polymer and resulted in efficient functionalization of the elastomer. © 2008 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 46: 8191–8199, 2008     

Synthesis and characterization of ether derivatives of brominated poly(isobutylene‐co‐isoprene)

Variations of the Williamson ether synthesis were employed to prepare a range of new derivatives of brominated poly(isobutylene‐co‐isoprene) (BIIR). Unambiguous characterization of the polymeric products was accomplished by spectroscopic comparisons to low‐molecular‐weight analogues derived from brominated 2,2,4,8,8‐pentamethyl‐4‐nonene, which served as a model for the reactive functionality found within BIIR. The substitution of bromide from BIIR occurred at moderate temperatures with stoichiometric amounts of quaternary ammonium phenoxide to yield O‐alkylation products in high yields. Simple mixtures of BIIR, KOH, and aliphatic alcohols generated the desired allylic ethers when heated above 110 °C in the absence of quaternary ammonium salts. Knowledge gained from these small‐molecule alkylations was used to prepare graft copolymers from BIIR and poly(ethylene oxide) through the exploitation of the apparent ability of polyethers to activate potassium alkoxides in nucleophilic substitutions. © 2005 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 44: 983–992, 2006