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 and luminescence characteristics of conjugated dendrimers with 2,4,6‐triaryl‐1,3,5‐triazine periphery

We have synthesized conjugated dendrimer with triazine peripheries, and their luminescence properties were investigated. The dendrimers consist of dendritic triazine wedges for electron transport, distyrylbenzene core as an emitting moiety, and t‐butyl peripheral groups for good processing properties. The dendrimers have LUMO values of about ?2.7 eV possibly because of the triazine moiety with high electron affinity. Photoluminescence study indicates that energy transfer occurs from the triazine wedges to the stilbene bridge, and finally to the core chromophore units due to a cascade decrease of bandgap from the peripheral wedge to core moiety. Therefore, the emission wavelength was determined by the structure of the core unit. The energy transfer efficiency of distyrylbenzene‐cored dendrimers was about 75 and 55% for Trz‐1GD‐DSB and Trz‐2GD‐DSB, respectively. A preliminary electroluminescence property also was investigated. © 2005 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 44: 254–263, 2006     

Second‐Order Nonlinear Optical Dendrimers and Dendronized Hyperbranched Polymers

Abstract : Second‐order nonlinear optical (NLO) dendrimers with a special topological structure were regarded as the most promising candidates for practical applications in the field of optoelectronic materials. Dendronized hyperbranched polymers (DHPs), a new type of polymers with dendritic structures, proposed and named by us recently, demonstrated interesting properties and some advantages over other polymers. Some of our work concerning these two types of polymers are presented herein, especially focusing on the design idea and structure–property relationship. To enhance their comprehensive NLO performance, dendrimers were designed and synthesized by adjusting their isolation mode, increasing the number of the dendritic generation, modifying their topological structure, introducing isolation chromophores, and utilizing the Ar‐Ar^F self‐assembly effect. To make full use of the advantages of both the structural integrity of dendrimers and the convenient one‐pot synthesis of hyperbranched polymers, DHPs were explored by utilizing low‐generation dendrons as big monomers to construct hyperbranched polymers. These selected works could provide valuable information to deeply understand the relationship between the structure and properties of functional polymers with dendritic structures, but not only limited to the NLO ones, and might contribute much to the further development of functional polymers with rational design.     

Practical syntheses of [1,3,5]‐triazine dendritic molecules on solid supports

A practical and divergent synthesis of supported [1,3,5]‐triazine dendritic molecules on Wang resin, PEGA resin, SynPhase? Lanterns, and silica gel is described. The alkylamine linkers used allow derivatization with functionality for both synthetic (e.g., supported reagent and scavenger activity) and chemical biology applications. The use of supported intermediates allows differentiation of symmetric linkers without the need for protecting group chemistry. The synthetic route uses inexpensive, readily available starting materials in a straightforward and scaleable strategy. © 2006 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 44: 2248–2259, 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     

Regioregular poly[3‐(4‐alkoxyphenyl)thiophene]s

An easy synthetic procedure for soluble poly[3‐(4‐alcoxyphenyl)thiophene]s is reported. The polymers present a high regioregularity degree as determined by both UV–vis spectra and ¹H and ¹³C NMR analysis. Furthermore, X‐ray powder diffraction analysis performed on films of the polymers suggests a π‐stacked packing structure of the macromolecules. Electrical characterization was performed on one of the synthesized polythiophenes on both undoped and doped (with FeCl₃ or iodine) films. The conductivity and charge‐carrier mobility were assessed by current–voltage and field effect measurements. Well‐structured polymer films were obtained simply via spin coating from chloroform solutions and without the need of further processing, unlike other regioregular polythiophenes reported in the literature. © 2007 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 45: 1758–1770, 2007     

Three 4,7‐diaryl‐2‐ethylsulfanylpyrazolo[1,5‐a][1,3,5]triazines

The molecular dimensions of 2‐ethylsulfanyl‐7‐(4‐methylphenyl)‐4‐phenylpyrazolo[1,5‐a][1,3,5]triazine, C₂₀H₁₈N₄S, (I), 7‐(4‐chlorophenyl)‐2‐ethylsulfanyl‐4‐phenylpyrazolo[1,5‐a][1,3,5]triazine, C₁₉H₁₅ClN₄S, (II), and 4,7‐bis(4‐chlorophenyl)‐2‐(ethylsulfanyl)pyrazolo[1,5‐a][1,3,5]triazine, C₁₉H₁₄Cl₂N₄S, (III), show evidence for some aromatic delocalization in the pyrazole rings. The conformations adopted by the ethylsulfanyl substituents are different in all three compounds. There are no hydrogen bonds in any of the crystal structures, but pairs of molecules in (II) and (III) are linked into centrosymmetric dimers by π‐stacking interactions.     

On triazoles XLV [1]. synthesis of 5,7‐diamino‐1,2,4‐triazolo[1,5‐a] [1,3,5]triazines

Dedicated to Professor András Messmer on the occasion of his 80^th birthday The reaction of differently substituted 5‐amino‐1,2,4‐triazoles ( 5 ) with isothiourea derivatives ( 3 ) to yield isomeric 5,7‐diamino‐1,2,4‐triazolo[1,5‐a][1,3,5]triazines ( 6 and 7 ), previously described as not proceeding in melt, was performed in different solvents as well as in the melt at 150‐160°. It was proved that the above reaction had rather general validity. The structure of isomers 6 and 7 were proved spectroscopically. The structure of 6/5 (Q = ethylamino) was corroborated with single crystal X‐ray diffraction determination, as well.     

Antimicrobial polymers containing melamine derivatives. II. Biocidal polymers derived from 2‐vinyl‐4,6‐diamino‐1,3,5‐triazine

Poly(2‐vinyl‐4,6‐diamino‐1,3,5‐triazine) (PVDAT) and a series of poly(styrene‐co‐2‐vinyl‐4,6‐diamino‐1,3,5‐triazine) (PS‐co‐VDAT) copolymers were synthesized via conventional free‐radical polymerizations. The polymer structures were confirmed by Fourier transform infrared, NMR, and elemental analysis. The molecular weights were determined by gel permeation chromatography studies, and the thermal properties were characterized by differential scanning calorimetry and thermogravimetric analysis. After treatment with chlorine bleach, PVDAT and PS‐co‐VDAT provided potent antimicrobial functions against multidrug‐resistant Gram‐negative and Gram‐positive bacteria. The antimicrobial functions were durable for longer than 3 months and rechargeable for more than 50 times. The structure–property relationship of the polymers was further discussed. © 2005 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 43: 4089–4098, 2005     

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 of dispiro[oxindole‐pyrrolidine]‐thiazolo[3,2‐a][1,3,5]triazines by 1,3‐dipolar cycloaddition

The 1,3‐dipolar cycloaddition of an azomethine ylide generated by a decarboxylative route from sarcosine and isatin to 7‐arylmethylidene‐3‐aryl‐3,4‐dihydro‐2H‐thiazolo[3,2‐a][1,3,5]triazin‐6(7H)‐ones afforded novel dispiro[oxindole‐pyrrolidine]‐thiazolo[3,2‐a][1,3,5]triazines in moderate yields. The structures of the products were determined and characterized thoroughly by NMR, MS, IR, and elemental analysis. The results of experiment indicated that this 1,3‐dipolar cycloaddition proceeded with high stereoselectivity and regioselectivity. J. Heterocyclic Chem., (2011).     

Dithieno[2,3‐d:2',3'‐d']benzo[1,2‐b:4,5‐b']dithiophene (DTBDAT)‐based copolymers for high‐performance organic solar cells

P(BDT‐TCNT) and P(DTBDAT‐TCNT) , which has an extended conjugation length, were designed and synthesized for applications in organic solar cell (OSCs). The solution absorption maxima of P(DTBDAT‐TCNT) with the extended conjugation were red‐shifted by 5–15 nm compared with those of P(BDT‐TCNT) . The optical band gaps and highest occupied molecular orbital (HOMO) energy levels of both P(BDT‐TCNT) and P(DTBDAT‐TCNT) were similar. The structure properties of thin films of these materials were characterized using grazing‐incidence wide‐angle X‐ray scattering and tapping‐mode atomic force microscopy, and charge carrier mobilities were characterized using the space‐charge limited current method. OSCs were formed using [6,6]‐phenyl‐C₇₁‐butyric acid methyl ester (PC₇₁BM) as the electron acceptor and 3% diphenylether as additive suppress aggregation. OSCs with P(BDT‐TCNT) as the electron donor exhibited a power conversion efficiency (PCE) of 4.10% with a short‐circuit current density of J_SC = 9.06 mA/cm², an open‐circuit voltage of V_OC = 0.77 V, and a fill factor of FF = 0.58. OSCs formed using P(DTBDAT‐TCNT) as the electron donor layer exhibited a PCE of 5.83% with J_SC = 12.2 mA/cm², V_OC = 0.77 V, and FF = 0.62. © 2016 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2016 , 54, 3182–3192     

Synthesis and characterization of new low band‐gap polymers containing electron‐accepting acenaphtho[1,2‐c]thiophene‐S,S‐dioxide groups

Two donor–acceptor conjugated polymers, PTSSO‐TT and PTSSO‐BDT, composed of acenaphtho[1,2‐c]thiophene ‐ S,S‐dioxide (TSSO) as a new electron acceptor and thienothiophene (TT) or benzo[1,2‐b:4,5‐b']dithiophene (BDT) as electron donors, were synthesized with Stille cross‐coupling reactions. The number‐averaged molecular weights (M_n) of PTSSO‐TT and PTSSO‐BDT were found to be 15100 and 26000 Da, with dispersity of 1.8 and 2.4, respectively. The band‐gap energies of PTSSO‐TT and PTSSO‐BDT are 1.56 and 1.59 eV, respectively. The HOMO levels of PTSSO‐TT and PTSSO‐BDT are ?5.4 and ?5.5 eV, respectively. These results indicate that the inclusion of TSSO accepting units into polymers is a very effective method for lowering their HOMO energy levels. The field‐effect mobilities of PTSSO‐TT and PTSSO‐BDT were determined to be 1.5 × 10^?3 and 4.5 × 10^?4 cm² V^?1 s^?1, respectively. A polymer solar cell device prepared with PTSSO‐TT as the active layer was found to exhibit a power conversion efficiency (PCE) of 3.79% with an open circuit voltage of 0.71 V under AM 1.5 G (100 mW cm^?2) conditions. © 2015 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2016 , 54, 498–506     

Donor–acceptor‐integrated conjugated polymers based on carbazole[3,4‐c:5,6‐c]bis[1,2,5]thiadiazole with tight π–π stacking for photovoltaics

An original strategy to construct a new donor–acceptor (D–A)‐integrated structure by directly imposing “pull” unit on the “push” moiety to form fused ring architecture has been developed, and poly{N‐alkyl‐carbazole[3,4‐c:5,6‐c]bis[1,2,5]thiadiazole‐alt‐thiophene} (PCBTT) with D–A‐integrated structure, in which two 1,2,5‐thiadiazole rings are fixed on carbazole in 3‐, 4‐ and 5‐, 6‐position symmetrically and thiophene is used as bridge, has been synthesized. The interaction between pull and push units has fine tuned the HOMO/LUMO energy levels, and the resulting copolymer covers the solar flux from 300 to 750 nm. The interaction between pull and push units is worth noting that due to the fused five rings inducing strong intermolecular interaction, an extremely short π–π stacking distance of 0.32 nm has been achieved for PCBTT both in powder and solid states. This is the shortest π–π stacking distance reported for conjugated polymers. Additionally, an obvious intramolecular charge transfer and energy transfer from donor units to acceptor units have been detected in this D–A integration. A moderate‐to‐high open‐circuit voltage of ～0.7 V in PCBTT:[6,6]‐phenyl‐C61 butyric acid methyl ester (PCBM) (w/w = 1/2) solar cells is achieved due to the low‐lying HOMO energy level of PCBTT. © 2012 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem, 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     

Synthesis and characterization of highly conjugated side‐group‐substituted benzo[1,2‐b:4,5‐b′]dithiophene‐based copolymer for use in organic solar cells

A new donor–acceptor (D–A) conjugated copolymer based on benzo[1,2‐b:4,5‐b′]dithiophene (BDT) and thieno[3,4‐c]pyrrole‐4,6‐dione (TPD) was synthesized via a Stille cross‐coupling reaction. A highly conjugated thiophene‐based side group, tris(thienylenevinylene) (TTV), was incorporated into each BDT unit to generate the two‐dimensional D–A copolymer (PBDT‐TTV). An alkoxy‐substituted BDT‐based TPD copolymer (PBDT‐OR) was synthesized using the same polymerization method for comparison. PBDT‐TTV thin films produced two distinct absorption peaks. The shorter wavelength absorption (458 nm) was attributed to the BDT units containing the TTV group, and the longer wavelength band (567–616 nm) was attributed to intramolecular charge transfer between the BDT donor and the TPD acceptor. The highest occupied molecular orbital energy levels of PBDT‐OR and PBDT‐TTV were calculated to be −5.53 and −5.61 eV, respectively. PBDT‐TTV thin films harvested a broad solar spectrum covering the range 300–700 nm. A comparison with the PBDT‐OR films revealed stronger interchain π–π interactions in the PBDT‐TTV films and, thus, a higher hole mobility. A polymer solar cell device prepared using PBDT‐TTV as the active layer was found to exhibit a higher power conversion efficiency than a device prepared using PBDT‐OR under AM 1.5 G (100 mW/cm²) conditions. © 2017 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2018 , 56, 653–660     

A versatile preparation of azobenzene‐dye functionalized colored polymer nanoparticles by surface modification

A series of stable and translucent colored nanolatex, that is, colloidal aqueous suspensions of dye‐tagged polymer nanoparticles (NPs) in the 15‐ to 20‐nm diameter range, have been prepared by covalent attachment of azobenzene chromophores to the surface of reactive NPs. Primary crosslinked NPs bearing chlorobenzyl groups were produced by microemulsion copolymerization of styrene and vinylbenzylchloride. Amine‐functionalized NPs were obtained after a second functionalization step with polyamines (cyclam and polypropyleneimine dendrimers of first and third generations). Dye‐doped particles were obtained by reacting pyridylazo‐dimethylaminobenzene (PADA) with chlorobenzyl‐NPs and by reacting amine‐reactive dimethylaminoazobenzene dyes (DABsyl, DAB‐ITC) as well as Disperse Red 1 acrylate with polyamine‐coated NPs. Regardless the dye solubility, the grafting readily proceeded in aqueous suspensions at room temperature in the presence of a cationic surfactant without added solvent. Purple, red, and orange suspensions (maximum absorption around 550, 500, 430 nm), with dye loads ranging from 0.3 to 1.2 mmol/g, corresponding to 400–1800 azobenzene residues per NP, are obtained. The reported results indicate that functional polymer NPs, with remarkably accessible multiple anchoring sites, are useful building blocks. © 2008 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 46: 3375–3386, 2008     

Solvent‐Free Microwave‐Assisted Synthesis of Novel 4‐Hetarylpyrazolo[1,5‐a][1,3,5]triazines

A series of novel 4‐hetaryl substituted pyrazolo[1,5‐a][1,3,5]triazines were synthesized by microwave assisted reaction between O,S‐diethyl hetaroylimidothiocarbonates and 5‐amino‐3‐aryl‐1H‐pyrazoles under solvent‐free conditions. This procedure led to the formation of mixtures of two new pyrazolotriazine derivatives in a 1:4 ratio, which were separated by column chromatography being their corresponding structures unambiguously established by spectroscopic and analytical techniques. Comparison of the reactions mediated by microwave irradiation and by conventional heating in solution of DMF showed that both procedures afforded the same mixtures of products, but the first approach required shorter reaction times and gave higher yields than the second one.     

Quaternized and Thiazole‐Functionalized Free Radical‐Generating Organometallic Dendrimers as Antimicrobial Platform against Multidrug‐Resistant Microorganisms

New macromolecules such as dendrimers are increasingly needed to drive breakthroughs in diverse areas, for example, healthcare. Here, the authors report hybrid antimicrobial dendrimers synthesized by functionalizing organometallic dendrimers with quaternary ammonium groups or 2‐mercaptobenzothiazole. The functionalization tunes the glass transition temperature and antimicrobial activities of the dendrimers. Electron paramagnetic resonance spectroscopy reveals that the dendrimers form free radicals, which have significant implications for catalysis and biology. In vitro antimicrobial assays indicate that the dendrimers are potent antimicrobial agents with activity against multidrug‐resistant pathogens such as methicillin‐resistant Staphylococcus aureus and vancomycin‐resistant Enterococcus faecium as well as other microorganisms. The functionalization increases the activity, especially in the quaternary ammonium group‐functionalized dendrimers. Importantly, the activities are selective because human epidermal keratinocytes cells and BJ fibroblast cells exposed to the dendrimers are viable after 24 h.

     

Controlled synthesis and chemical modification of unsaturated aliphatic (Co)polyesters based on 6,7‐dihydro‐2(3H)‐oxepinone

A pure unsaturated cyclic ester, 6,7‐dihydro‐2(3H)‐oxepinone (DHO2), was prepared by a new synthetic route. The copolymerization of DHO2 with ?‐caprolactone (?CL) was initiated by aluminum isopropoxide [Al(OⁱPr)₃] at 0 °C as an easy way to produce unsaturated aliphatic polyesters with nonconjugated C?C double bonds in a controlled manner. The chain growth was living, as certified by the agreement between the experimental molecular weight at total monomer conversion and the value predicted from the initial monomer/initiator molar ratio. The polydispersity was reasonably low (weight‐average molecular weight/number‐average molecular weight ≤ 1.2). The homopolymerization of DHO2 was, however, not controlled because of fast intramolecular transesterification. Copolymers of DHO2 and ?CL were quantitatively oxidized with the formation of epoxides containing chains. The extent of the epoxidation allowed the thermal properties and thermal stability of the copolyesters to be modulated. The epoxidized copolyesters were successfully converted into thioaminated chains, which were then quaternized into polycations. No degradation occurred during the chemical modification. © 2002 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 40: 2286–2297, 2002