Dibenzophenazine derivatives as visible photosensitizers for diaryliodonium salts

The use of two dibenzo[a,c]phenazine derivatives, 10,13‐bis(2,3‐dihydrothieno[3,4‐b][1,4]dioxin‐5‐yl)dibenzo[a,c]phenazine and 10,13‐bis(4‐hexylthiophen‐2‐yl)dibenzo[a,c]phenazine are reported as photosensitizers for diaryliodonium salt photoinitiators. Novel dyes based on the dibenzo[a,c]phenazine skeleton are shown to be efficient in carrying out the cationic photopolymerizations. Representative examples of different types of monomers including epoxide, and vinyl monomers are polymerized in the presence of the photosensitizers and diphenyliodonium hexafluorophosphate (Ph₂I⁺PF). Polymerizations are initiated at room temperature using long wavelength UV and visible light, and monitored by optical pyrometry. The photopolymerization of an epoxide monomer via solar irradiation is also demonstrated. © 2011 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem, 2011     

Electrochemical synthesis of PEDOT derivatives bearing imidazolium‐ionic liquid moieties

Novel poly(3,4‐ethylenedioxythiophene) (PEDOT) polymers bearing imidazolium‐ionic liquid moieties were synthesized by electrochemical polymerizations. For this purpose, new functional monomers were synthesized having an 3,4‐ethylenedioxythiophene (EDOT) unit and an imidazolium‐ionic liquid with different anions such as tetrafluoroborate (BF), bis(trifluoromethane)sulfonimide ((CF₃SO₂)₂N^?), and hexafluorophosphate (PF). Next, polymer films were obtained by electrochemical synthesis in dicholoromethane solutions. Obtained polymers were characterized, revealing the characteristics of PEDOT in terms of electrochemical and spectroelectrochemical properties, FTIR, ¹H NMR, and AFM microscopy. Interestingly, the hydrophobic character of electropolymerized films could be modified depending on the anion type. The hydrophobicity followed the trend PF > (CF₃SO₂)₂N^? > BF > pure PEDOT as determined by water contact angle measurements. Furthermore, the polymers could be dissolved in a range of polar organic solvents such as dimethylformamide, propylene carbonate, and dimethyl sulfoxide making these polymers interesting candidates for wet processing methods. © 2009 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 47: 3010–3021, 2009     

Visible light induced free radical promoted cationic polymerization using thioxanthone derivatives

The free radical promoted cationic polymerization cyclohexene oxide (CHO), was achieved by visible light irradiation (λ_inc = 430–490 nm) of methylene chloride solutions containing thioxanthone‐fluorene carboxylic acid (TX‐FLCOOH) or thioxanthone‐carbazole (TX‐C) and cationic salts, such as diphenyliodonium hexafluorophosphate (Ph₂I⁺PF) or silver hexafluorophosphate (Ag⁺PF) in the presence of hydrogen donors. A feasible initiation mechanism involves the photogeneration of ketyl radicals by hydrogen abstraction in the first step. Subsequent oxidation of ketyl radicals by the oxidizing salts yields Bronsted acids capable of initiating the polymerization of CHO. In agreement with the proposed mechanism, the polymerization was completely inhibited by 2,2,6,6‐tetramethylpiperidinyl‐1‐oxy and di‐2,6‐di‐tert‐butylpyridine as radical and acid scavengers, respectively. Additionally polymerization efficiency was directly related to the reduction potential of the cationic salts, that is, Ag⁺PF (E = +0.8 V) was found to be more efficient than Ph₂I⁺PF (E = ?0.2 V). In addition to CHO, vinyl monomers such as isobutyl vinyl ether and N‐vinyl carbazole, and a bisepoxide such as 3,4‐epoxycyclohexyl‐3′,4′‐epoxycyclohexene carboxylate, were polymerized in the presence of TX‐FLCOOH or TX‐C and iodonium salt with high efficiency. © 2011 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem, 2011     

Synthesis,properties, and field effect transistor characteristics of new thiophene‐[1,2,5]thiadiazolo[3,4‐g]quinoxaline‐thiophene‐based conjugated polymers

Four new conjugated copolymers based on the moiety of bis(4‐hexylthiophen‐2‐yl)‐6,7‐diheptyl‐[1,2,5]thiadiazolo[3,4‐g]quinoxaline (BTHTQ) were synthesized and characterized, including poly(6,7‐diheptyl‐4,9‐bis(4‐hexylthiophen‐2‐yl)‐[1,2,5]thiadiazolo[3,4‐g]quinoxaline) (PBTHTQ), poly‐(6,7‐diheptyl‐4,9‐bis(4‐hexylthiophen‐2‐yl)‐[1,2,5]thiadiazolo‐[3,4‐g]quinoxaline‐alt‐2,5‐thiophene) (PTTHTQ), poly(6,7‐diheptyl‐4,9‐bis(4‐hexylthiophen‐2‐yl) [1,2,5]‐thiadiazolo‐[3,4‐g]quinoxaline‐alt‐9,9‐dioctyl‐2,7‐fluore‐ne) (PFBTHTQ), and poly(6,7‐diheptyl‐4,9‐bis(4‐hexylthiophen‐2‐yl)‐[1,2,5]thiadiazolo[3,4‐g]quinoxaline‐alt‐1,4‐bis(decyloxy)phenylene) (PPBTHTQ). The λ_max of PBTHTQ, PTTHTQ, PFBTHTQ, and PPBTHTP thin films was shown at 780, 876, 734, and 710 nm, respectively, with the corresponding optical band gaps (E) of 1.31, 1.05, 1.40, and 1.43 eV. The relatively small band gaps of the synthesized polymers suggested the significance of intramolecular charge transfer between the donor and TQ moiety. The estimated hole mobilities of PBTHTQ, PTTHTQ, and PFBTHTQ‐based field effect transistor devices using CHCl₃ solvent were 8.5 × 10^?5, 8.5 × 10^?4, and 2.8 × 10^?5 cm² V^?1 s^?1, respectively, but significantly enhanced to 1.6 × 10^?4, 3.8 × 10^?3, and 1.5 × 10^?4 cm² V^?1 s^?1 using high boiling point solvent of chlorobenzene (CB). The higher hole mobility of PTTHTQ than the other two copolymers was attributed from its smaller band gap or ordered morphology [wormlike (chloroform) or needle‐like (CB)]. The characteristics of small band gap and high mobility suggest the potential applications of the BTHTQ‐based conjugated copolymers in electronic and optoelectronic devices. © 2008 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 46: 6305–6316, 2008     

Lactide polymerization activity of alkoxide,phenoxide, and amide derivatives of yttrium(III) arylamidinates

In quest of new, single‐site catalysts for cyclic ester polymerizations, a series of mononuclear yttrium(III) complexes of N,N′‐bis(trimethylsilyl)benzamidinate ([L^TMS]⁻) and hindered N,N′‐bis‐(2,6‐dialkylaryl)toluamidinates ([L^Et]⁻, aryl = Et₂C₆H₃, and [L^iPr]⁻, aryl = ⁱPr₂C₆H₃) were synthesized and characterized by X‐ray diffraction: LY(μ‐Cl)₂Li(TMEDA) ( 1 ), LY(OC₆H₂^tBu₂Me) ( 2 ), LY(OC₆H₃Me₂)₂Li(THF)₄ ( 3 ), LY(μ‐O^tBu)₂Li(THF) ( 4 ), L^iPrY[N(SiMe₂H)₂]₂(THF) ( 5 ), LY(THF)(Cl)(μ‐Cl)Li(THF)₃ ( 6 ), and LY[N(SiMe₂H)₂] ( 7 ). Coordination numbers ranging from five to seven were observed, and they appeared to be controlled by the steric bulk of the supporting amidinate and alkoxide, phenoxide, or amide coligands. Complexes 2 – 5 and 7 are active catalysts for the polymerization of D,L ‐lactide (e.g., with 2 and added benzyl alcohol, 1000 equiv of D,L ‐lactide were polymerized at room temperature in less than 1 h, with polydispersities less than 1.5). The neutral complexes 2 , 5 , and 7 were more effective than the anionic complexes 3 and 4 . In addition, the presence of the more hindered amidinate ligands [L^Et]⁻ and [L^iPr]⁻ on yttrium‐amides slowed the polymerizations ( 7 < 5 < Y[N(SiMe₂H)₂]₃). © 2000 John Wiley & Sons, Inc. J Polym Sci A: Polym Chem 39: 284–293, 2001     

A chiral polymer‐based turn‐on fluorescent sensor for specific recognition of hydrogen sulfate

A new kind of polymeric chemosensor containing chiral naphthaldimine moiety in the side chain was synthesized by the reversible addition‐fragmentation chain transfer polymerization of N‐{[2‐(4‐vinylbenzyloxy)‐1‐naphthyl]‐methylene}‐(S)‐2‐phenylglycinol (VNP). The resulting polymers (PVNP) showed high selectivity for hydrogen sulfate relative to other anions including F^?, Cl^?, Br^?, H₂PO, CH₃CO, and NO in tetrahydrofuran (THF) solution as judged from UV?vis, fluorescence, and circular dichroism spectrophotometric titrations. Compared with its monomer, the polymer has proven to be more attractive for detection of HSO in terms of sensitivity and reproducibility. Upon addition of the anion it gives remarkable spectral responses concomitant with detectable color change from colorless to pale yellow. Furthermore, the HSO‐induced CD or fluorescence signal can be totally reversed with addition of base and eventually recovered the initial state, leading to a reproducible molecular switch with two distinguished “on” and “off” states. © 2012 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem, 2012     

Anionic ring‐opening polymerization of propylene oxide in the presence of phosphonium catalysts

Anionic ring‐opening polymerization of propylene oxide in the presence of potassium alcoholate initiator was accelerated by addition of the bulky phosphonium salt tetrakis[cyclohexyl(methyl)amino]phosphonium‐tetrafluoroborate. Dipropylene glycol (DPG) was partially deprotonated (5%) and used as an initiator for the polymerization performed at 100 °C at normal pressure. The delocalization of the positive charge over five atoms promoted the formation of a separated ion pair, thus enhancing nucleophilicity and reactivity. Compared with those of polyaminophosphazenes and tetrabutylphosphonium cation, the average propagation rates increased in the order of Bu₄P⁺, K⁺, P, P, and ^tBuP₄H⁺. DP_n for the polymers was in the range of 20–64. Characterization of poly(propylene oxide)s by means of ¹H NMR, size exclusion chromatography (SEC), and matrix‐assisted laser desorption/ionization time‐of‐flight mass spectrometry (MALDI‐TOF‐MS) showed low polydispersities (M_w/M_n) without any byproducts or impurities. The M_w/M_n obtained was 1.03–1.09 (MALDI‐TOF‐MS) and 1.11–1.15 (SEC), respectively. Values calculated from titration of the hydroxyl groups showed good agreement. Determination of the total degree of unsaturation in the range of 13–60 mmol/kg indicated larger amounts with increasing polymerization rates. © 2002 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 40: 864–873, 2002; DOI 10.1002/pola.10163     

Non‐transition metal‐catalyzed living radical polymerization of vinyl chloride initiated with iodoform in water at 25 °C

Non‐transition metal‐catalyzed living radical polymerization (LRP) of vinyl chloride (VC) in water at 25–35 °C is reported. This polymerization is initiated with iodoform and catalyzed by Na₂S₂O₄. In water, S₂O dissociates into SO that mediates the initiation and reactivation steps via a single electron transfer (SET) mechanism. The exchange between dormant and active propagating species also includes the degenerative chain transfer to dormant species (DT). In addition, the SO₂ released from SO during the SET process can add reversibly to poly(vinyl chloride) (PVC) radicals and provide additional transient dormant ～SO radicals. This novel LRP proceeds mostly by a combination of competitive SET and DT mechanisms and, therefore, it is called SET‐DTLRP. Telechelic PVC with a number‐average molecular weight (M_n) = 2,000–55,000, containing two active ～CH₂? CHClI chain ends and a higher syndiotacticity than the commercial PVC were obtained by SET‐DTLRP. This PVC is free of structural defects and exhibits a higher thermal stability than commercial PVC. SET‐DTLRP of VC is carried out under reaction conditions related to those used for its commercial free‐radical polymerization. Consequently, SET‐DTLRP is of technological interest both as an alternative commercial method for the production of PVC with superior properties as well as for the synthesis of new PVC‐based architectures. © 2004 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 42: 6267–6282, 2004     

Kinetics and mechanism of the cationic polymerization of trioxane. I. Crystallization during polymerization

Cationic polymerizations of trioxane in 1,2‐ethylene dichloride and benzene were heterogeneous and reversible. Phase separation accompanying with crystallization occurred during the polymerization. Three morphological changes were found in the course of the polymerization as were investigated by dilatometry and precipitation method. Based on the findings of morphological changes and three reversible processes for the polymerization, a rate equation was proposed to describe the polymerization. The proposed rate equation was fairly good in describing the experimental data, and kinetics constants including K_p, K_d, K_p′, K_d′, M, M, and K_dis/K_cr for the polymerization at 30, 40, and 50°C in 1,2‐ethylene dichloride and benzene were obtained. Factors that affected the kinetics constants were discussed. © 1999 John Wiley & Sons, Inc. J Polym Sci A: Polym Chem 37: 483–492, 1999     

Synthesis and characterizations of well‐defined branched polymers with AB2 branches by combination of RAFT polymerization and ROP as well as ATRP

A well‐defined branched copolymer with PLLA‐b‐PS₂ branches was prepared by combination of reversible addition‐fragmentation transfer (RAFT) polymerization, ring‐opening polymerization (ROP), and atom transfer radical polymerization (ATRP). The RAFT copolymerization of methyl acrylate (MA) and hydroxyethyl acrylate (HEA) yielded poly(MA‐co‐HEA), which was used as macro initiator in the successive ROP polymerization of LLA. After divergent reaction of poly(MA‐co‐HEA)‐g‐PLLAOH with divergent agent, the macro initiator, poly(MA‐co‐HEA)‐g‐PLLABr₂ was formed in high conversion. The following ATRP of styrene (St) produced the target polymer, poly(MA‐co‐HEA)‐g‐(PLLA‐b‐PS₂). The structures, molecular weight, and molecular weight distribution of the intermediates and the target polymers obtained from every step were confirmed by their ¹H NMR and GPC measurements. DSC results show one T = 3 °C for the poly(MA‐co‐HEA), T = ?5 °C, T= 122 °C, and T = 157 °C for the branched copolymers (poly(MA‐co‐HEA)‐g‐PLLA), and T = 51 °C, T = 116 °C, and T = 162 °C for poly(MA‐co‐HEA)‐g‐(PLLA‐b‐PS₂). © 2005 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 44: 549–560, 2006     

Synthesis and characterization of new polymeric ionic liquid microgels

A new two‐step route toward the synthesis of polymeric ionic liquid microgel particles is presented. In the first step, hydrophilic microparticles were prepared by the concentrated emulsion polymerization of the ionic liquid 1‐vinyl‐3‐ethylimidazolium bromide in the presence of small amounts of N,N‐dimethylenebisacrylamide as a crosslinking agent. In the second step, the bromide anion was exchanged in water with different anions such as BF, CF₃SO, (CF₃SO₂)₂N^?, (CF₃CF₂SO₂)₂N^?, and dodecylbenzenesulfonate, and this resulted in the coagulation of the microparticles, which were easily recovered by filtration. The obtained polymeric ionic liquid microparticles could be swollen in a very broad range of organic solvents, including apolar organic solvents. As an application, glucose oxidase was encapsulated inside polymeric ionic liquid microparticles, which were used in an amperometric biosensor. The response of the biosensor showed excellent values that strongly depended on the nature of the polymeric ionic liquid counteranion in the order of Br^? > BF > (CF₃SO₂)₂N^?. © 2006 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 44: 3958–3965, 2006     

Thermal and ion transport properties of hydrophilic and hydrophobic polymerized styrenic imidazolium ionic liquids

Polymerized ionic liquids (PILs) are a platform for fundamental studies of structure‐property relationships in single ion conductors, with potential applications in energy storage and conversion. The synthesis, thermal properties, and ionic conductivities of homologous, narrow dispersity styrenic PILs are described. Hydrophilic poly(4‐vinylbenzyl alkylimidazolium chloride) (PVBn(alkyl)ImCl) homopolymers with constant average degrees of polymerization were synthesized by post‐synthetic functionalization of a poly(4‐vinylbenzyl chloride) (M_n = 15.9 kg/mol, M_w/M_n = 1.34) master batch with N‐alkylimidazoles (alkyl = ? CH₃ (Me), ? C₄H₉ (Bu), and ? C₆H₁₃ (Hex)). The chloride counterions of PVBnHexImCl were exhaustively metathesized with BF, PF, and bis(trifluoromethanesulfonyl)imide (TFSI^?) to yield a series of hydrophobic PILs. Thermogravimetric analyses indicate that PVBn(alkyl)ImCl homopolymers are unstable above 220 °C, whereas the hydrophobic PILs remain stable up to 290 °C. The glass transition temperatures (T_g) decrease with both increasing alkyl side‐chain length and increasing counterion size, exemplified by T_g = 9 °C for PVBnHexImTFSI. Hydrophilic PILs exhibit high ionic conductivities (as high as ～0.10 S cm^?1) that depend on the relative humidity, water uptake, and the PIL side chain length. The hydrophobic PILs exhibit lower conductivities (up to ～5 × 10^?4 S cm^?1) that depend predominantly on the polymer T_g, however, counterion size and symmetry also contribute. © 2011 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 49: 1287–1296, 2011     

Sequential photodecomposition of bisacylgermane type photoinitiator: Synthesis of block copolymers by combination of free radical promoted cationic and free radical polymerization mechanisms

A block copolymer of cyclohexene oxide (CHO) and styrene (St) was prepared by using bifunctional visible light photoinitiator dibenzoyldiethylgermane (DBDEG) via a two‐step procedure. The bifunctionality of the photoinitiator pertains to the sequential photodecomposition of DBDEG through acyl germane bonds. In the first step, photoinitiated free radical promoted cationic polymerization of CHO using DBDEG in the presence of diphenyliodonium hexafluorophosphate (Ph₂I⁺PF) was carried out to yield polymers with photoactive monobenzoyl germane end groups. These poly(cyclohexene oxide) (PCHO) prepolymers were used to induce photoinitiated free radical polymerization of styrene (St) resulting in the formation of poly(cyclohexene oxide‐block‐styrene) (P(CHO‐b‐St)). Successful blocking has been confirmed by a strong change in the molecular weight of the prepolymer and the block copolymer as well as NMR, IR, and DSC spectral measurements. © 2009 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 47: 4793–4799, 2009     

Melt‐state polymer chain dimensions as a function of temperature

The unperturbed chain dimensions (〈R²〉_o/M) of cis/trans‐1,4‐polyisoprene, a near‐atactic poly(methyl methacrylate), and atactic polyolefins were measured as a function of temperature in the melt state via small‐angle neutron scattering (SANS). The polyolefinic materials were derived from polydienes or polystyrene via hydrogenation or deuteration and represent structures not encountered commercially. The parent polymers were prepared via lithium‐based anionic polymerizations in cyclohexane with, in some cases, a polymer microstructure modifier present. The polyolefins retained the near‐monodisperse molecular weight distributions exhibited by the precursor materials. The melt SANS‐based chain dimension data allowed the evaluation of the temperature coefficients [dln 〈R²〉_o/dT(κ)] for these polymers. The evaluated polymers obeyed the packing length (p)‐based expressions of the plateau modulus, G = kT/np³ (MPa), and the entanglement molecular weight, M_e = ρN_anp³ (g mol^?1), where n_t denotes the number (～21) of entanglement strands in a cube with the dimensions of the reptation tube diameter (d_t) and ρ is the chain density. The product np³ is the displaced volume (V_e) of an entanglement that is also expressible as pd or kT/G. © 2002 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 40: 1768–1776, 2002     

Cyanoxyl‐mediated free‐radical polymerization of acrylic acid: Its scope and limitations

This work examines the scope and limitations of the cyanoxyl (^·OC?N)‐mediated free‐radical polymerization of acrylic acid (AA) with respect to the criteria of livingness. Cyanoxyl persistent radicals were generated in situ through the reaction between arenediazonium salts (X? C₆H₄N?N^⊕BF, where X is H, OCH₃, Cl, or NO₂) and sodium cyanate (NaOCN). This article thoroughly discusses the role played by such oxygen‐centered radicals in the polymerization process; it particularly focuses on the influence of the concentration and nature of the diazonium salt, the solvent, and the temperature on features such as the variations of ln([M]₀/[M]) versus time (where [M]₀ is the initial monomer concentration and [M] is the monomer concentration), the number‐average molar mass versus conversion, and the polydispersity versus conversion in cyanoxyl‐mediated free‐radical polymerizations of AA. Cyanoxyl‐terminated samples were used as macroinitiators for the polymerization of methyl methacrylate to generate poly(acrylic acid)‐b‐poly(methyl methacrylate) block copolymers. © 2004 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 43: 519–533, 2005     

Unexpected reactivity for the RAFT copolymerization of oligo(ethylene glycol) methacrylates

Homo‐ and copolymers of di(ethylene glycol) methyl ether methacrylate (DEGMA) and oligo(ethyleneglycol) methyl ether methacrylate (OEGMA₁₁₀₀) were synthesized with various chain lengths via reversible addition fragmentation chain transfer (RAFT) polymerization in ethanol using [M]/[RAFT] ratios of 100 and 200. Kinetic investigations on the homo‐ and copolymerization of these monomers were performed using a parallel synthesizer resulting in well‐defined polymers with polydispersity indices mostly below 1.3. The polymerization kinetics are presented and discussed in detail surprisingly revealing that the DEGMA homopolymerization is slower than the OEGMA₁₁₀₀ homopolymerization. Transfer coefficients c were estimated to be ～0.5 for the RAFT polymerization of both DEGMA and OEGMA₁₁₀₀ resulting in hybrid behavior at the beginning of the polymerizations. Subsequent copolymerization also revealed fast incorporation of the OEGMA₁₁₀₀ and relatively slow incorporation of DEGMA resulting in well‐defined copolymers with a molecular weight up to 100 kDa and polydispersities around 1.20. © 2009 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 47: 2811–2820, 2009     

Improving the control of styrene polymerization at 60 °C using a dialkylated α‐hydrogenated nitroxide

A new dialkylated α‐hydrogenated linear nitroxide and the corresponding 1‐phenylethyl alkoxyamine were synthesized in two and three steps, respectively. The alkoxyamine was involved in the polymerization of styrene at 60 °C, and the in situ concentration of nitroxide was monitored by electron spin resonance spectroscopy. The enhanced characteristics of these new alkylated alkoxyamine and nitroxide (k = 1.5 × 10^?4 s^?1 and k = 5.7 × 10⁴ L mol^?1 s^?1) yielded a monomer consumption one order of magnitude higher than styrene thermal polymerization. This resulted in well‐defined polystyrenes up to 70,000 g mol^?1 and the observation of a control occurring through the establishment of the radical persistent effect, that is, ln([M]₀/[M]) = t^2/3. Experimentally determined kinetic constants were involved in PREDICI modelings to investigate the influence of temperature and initial alkoxyamine concentration on the kinetics as well as on the livingness and the controlled character of the polymerization. © 2012 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem, 2012     

Cp2TiCl‐catalyzed living radical polymerization of styrene initiated from peroxides

The effects of the reaction conditions and nature of the initiator were investigated in the Cp₂Ti(III)Cl‐catalyzed living radical polymerization of styrene initiated by benzoyl peroxide (BPO), tert‐butyl peroxide (TBPO), tert‐butyl peroxybenzoate (TBPOB), dicumyl peroxide (CPO), and tert‐butylperoxy 2‐ethylhexyl carbonate (TBPOEHC). The reversible termination of the growing chains with Cp₂Ti(III)Cl affords a linear dependence of molecular weight on conversion over a wide range of temperatures (60–120 °C) with an optimum in polydispersity (M_w/M_n < 1.2) for St/BPO/Cp₂TiCl₂/Zn = 100/1/3/6 at 60–90 °C. The similarity of the kinetic parameters from polymerizations initiated by peroxides with vastly different half‐life times (t = 1 h, t = 543 h) and the minimum peroxide/Ti = 1/2 ratio required for a living process indicate that initiation occurs primarily by the redox reaction of the peroxide with Cp₂Ti(III)Cl rather than peroxide thermal decomposition. This is consistent with one Ti equivalent consumed in the redox initiation and the second one utilized in the reversible termination of the growing chains. Qualitatively, based on the livingness of the process, these initiators ranked as BPO > TBPOB ～ TBPO > CPO > TBPOEHC. © 2005 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 44: 1106–1116, 2006     

Donor–acceptor alternating π‐conjugated polymers containing Di(thiophen‐2‐yl)pyrene and 2,5‐Bis(2‐octyldodecyl)pyrrolo[3,4‐c]pyrrole‐1,4(2H,5H)‐dione for organic thin‐film transistors

New diketopyrrolopyrrole (DPP)‐containing conjugated polymers such as poly(2,5‐bis(2‐octyldodecyl)‐3‐(5‐(pyren‐1‐yl)thiophen‐2‐yl)‐6‐(thiophen‐2‐yl)pyrrolo[3,4‐c]pyrrole‐1,4(2H,5H)‐dione) (P(DTDPP‐alt‐(1,6)PY)) and poly(2,5‐bis(2‐octyldodecyl)‐3‐(5‐(pyren‐2‐yl)thiophen‐2‐yl)‐6‐(thiophen‐2‐yl)pyrrolo[3,4‐c]pyrrole‐1,4(2H,5H)‐dione) (P(DTDPP‐alt‐(2,7)PY)) were successfully synthesized via Suzuki coupling reactions under Pd(0)‐catalyzed conditions. P(DTDPP‐alt‐(2,7)PY), incorporating 2,5‐bis(2‐octyldodecyl)‐3,6‐di(thiophen‐2‐yl)pyrrolo[3,4‐c]pyrrole‐1,4(2H,5H)‐dione (DTDPP) at the 2,7‐position of a pyrene ring showed a lower band‐gap energy (E. = 1.65 eV) than the 1,6‐substituted analog, P(DTDPP‐alt‐(1,6)PY) (E = 1.71 eV). The energies of the molecular frontier orbitals of the substituted polymers were successfully tuned by changing the anchoring position of DTDPP from the 1,6‐ to the 2,7‐position of the pyrene ring. An organic thin‐film transistor fabricated using the newly synthesized P(DTDPP‐alt‐(2,7)PY), as a semiconductor material exhibited a maximum mobility of up to 0.23 cm² V^?1 s^?1 (I_on/off ～ 10⁶), which was much larger than that obtained using P(DTDPP‐alt‐(1,6)PY). This distinction is attributed to morphological differences in the solid state arising from differences between the geometrical configurations of DTDPP and the pyrene ring. In addition, the organic phototransistor devices made of P(DTDPP‐alt‐(2,7)PY) showed interesting photoinduced enhancement of drain current when irradiating the excitation light whose intensity is very small. Based on the photoinduced effect on I_DS, photocontrolled memory could be realized under the variation of gate voltages. © 2013 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem, 2013