Cationic Polymerization of Epoxides using Novel Xanthenyl Phosphonium Salts as Thermo-latent Initiator

The present article describes the effect of steric and electronic factors on the efficiency of initiators based on novel xanthenyl phosphonium salts for cationic polymerization of epoxide monomers. 2-substituted (I_H, I_Cl, I_Me, and I_OMe) xanthenyl phosphonium hexafluoroantimonate were synthesized and characterized by NMR (¹H, ¹³C and ³¹P) and IR spectroscopy. The order of initiator activity in polymerization of glycidyl phenyl ether (GPE), was found as I_H> I_Cl>I_Me>I_OMe. To understand the effect of steric factor, the polymerization of cyclohexene oxide (CHO) was performed and the order of activity was found as I_Cl>I_H>I_Me >I_OMe. All the initiators were found to be latent at ambient temperature and initiates polymerization on thermal initiation. The order of initiator activity was influenced by electronic and steric factors in the system. The thermal stability of these salts was measured by Thermo gravimetric analysis (TGA). The solubility of the initiators in various organic solvents and epoxy monomers is also discussed.     

Hydrazinium salts as thermally latent initiators in the polymerization of glycidyl phenyl ether

Novel hydrazinium salts, N,N‐dimethyl N‐benzyl N′‐benzyl N′‐benzoyl hydrazinium hexafluoroantimonate (2) and N,N‐dimethyl N‐benzyl N′‐(2‐propyl) N′‐benzoyl hydrazinium hexafluoroantimonate (3) were synthesized from hydrazinium salt (1) with the corresponding alcohol. Their initiator activities were examined in the polymerization of glycidyl phenyl ether (GPE). The polymerization of GPE did not proceed with 2 and 3 below 60 and 100°C but proceeded rapidly above those temperatures, respectively. It was found that 1–3 served as thermally latent initiators in the polymerization of GPE. The initiating species and terminating species were identified as the proton or alkyl cation and aminimide, respectively. © 2005 Wiley Periodicals, Inc. J Appl Polym Sci 95: 1439–1442, 2005     

Novel piperidinium salts as latent initiators for cationic polymerization of epoxide and vinyl ether

Novel dibenzylpiperidinium salts with nonnucleophilic anions (DBPi‐SbF₆, DBPi‐PF₆) have been prepared as latent cationic initiators. Utility of these salts in the photo and thermal‐induced cationic polymerizations of epoxide and vinyl ether monomer systems has been studied. The new initiator, DBPi‐SbF₆ showed good solubility, high reactivity, and high thermal latency for polymerizations of epoxide and vinyl ether monomers with only 1 wt % of concentration. Cationic polymerization of vinyl ether monomer was significantly faster than epoxide monomer by the synthesized initiators. This article describes the synthesis, characterization, and activity of novel initiators. © 2008 Wiley Periodicals, Inc. J Appl Polym Sci, 2009     

Polymerization of allyl methacrylate with wool fabric using different initiators

Polymerization of allyl methacrylate (AMA) with wool fabrics using different initiators, namely, potassium persulphate, Fe²⁺? H₂O₂, benzoyl peroxide, ceric ammonium nitrate, and vanadium pentanitrate, was investigated. The percent of polymer add-on depends upon the type and concentration of the initiator. Addition of metallic salts such as Fe³⁺ to the polymerization system enhances polymerization significantly when benzoyl peroxide and potassium persulphate are used independently as initiator. The opposite holds true for ceric ammonium nitrate and vanadium pentanitrate. With Fe²⁺? H₂O₂, on the other hand, the enhancement is marginal. Also studied was the incorporation of Li⁺, Cu⁺⁺, and Fe³⁺ at different concentrations in AMA—wool–benzoyl peroxide polymerization systems. Determination of the polymer add-on on the basis of double bond analysis revealed that the remained double bond is governed by the magnitude of the polymer add-on as well as by the type of initiator.     

Curing of epoxides with O,O‐di‐t‐butyl phenylphosphonate as thermally latent initiator

The polymerization of glycidyl phenyl ether (GPE) was examined with O,O‐di‐t‐butyl phenylphosphonate (BP) as an initiator in the presence of several Lewis acids, ammonium salts, and methyl cyanoacetate. BP served as an excellent thermally latent initiator in the polymerization of GPE in the presence of ZnCl₂ and Zn(acac)₂. Epikote 828 was cured with BP (5 mol %) in the presence of ZnCl₂ at 150°C to afford the solvent‐insoluble gelled epoxy resin quantitatively, which was thermally more stable than was the one cured without ZnCl₂. No curing took place at room temperature for 7 months. © 2001 John Wiley & Sons, Inc. J Appl Polym Sci 81: 2347–2351, 2001     

Synthesis of polyacrylonitrile via reverse atom transfer radial polymerization (ATRP) initiated by diethyl 2,3‐dicyano‐2,3‐diphenylsuccinate,FeCl3, and triphenylphosphine

The reverse atom transfer radical polymerization (RATRP) technique using FeCl₃/triphenyl‐phosphine (PPh₃) complex as a catalyst was applied to the living radical polymerization of acrylonitrile (AN). A hexa‐substituted ethane thermal iniferter, diethyl 2,3‐dicyano‐2,3‐diphenylsuccinate (DCDPS), was first used as the initiator in this iron‐based RATRP initiation system. A FeCl₃ to PPh₃ ratio of 1:3 not only gives the best control of molecular weight and its distribution but also provides a rather rapid reaction rate. The rate of polymerization increases with increasing the polymerization temperature and the apparent activation energy was calculated to be 54.9 kJ mol^?1. Because the polymers obtained were end‐functionalized by chlorine atoms, they were used as macro‐initiators to proceed the chain extension polymerization in the presence of an FeCl₂/PPh₃ catalyst system via a conventional ATRP process. Copyright © 2005 Society of Chemical Industry     

Photocationic and radical polymerizations by novel N‐phenacylammonium salts

Novel N‐phenacylammonium salts [N‐(α‐benzoylbenzyl)‐, N‐(1‐benzoylethyl)‐, N‐phenacyl‐, pyrazinium, 3‐bromoquinolinium, benzothiazolium, or p‐cyanopyridinium hexafluoroantimonates] were synthesized by the reaction of α‐benzoylbenzyl bromide, 2‐bromopropiophenone or phenacylbromide, and the corresponding N‐hetero aromatic compound, followed by anion exchange with KSbF₆. These N‐phenacylammonium salts showed higher activity than previously reported N‐benzyl‐2‐cyanopyridinium hexafluoroantimonate in the photopolymerization of epoxides. Further, these N‐phenacylammonium salts served as photoradical and thermal cationic initiators as well as photocationic initiators. © 2004 Wiley Periodicals, Inc. J Appl Polym Sci 91: 3470–3476, 2004     

Kinetic and Thermodynamic Studies of Emulsion Polymerization of a Sugar Monomer by Calorimetry with Compensation Heating and Differential Cooling

The kinetic and thermodynamic features of free‐radical batch emulsion polymerization of a sugar monomer (3‐MDG) and butyl acrylate (BA) were investigated in a power compensation calorimeter. The homopolymerizations as well as the copolymerization have been studied. The overall activation energy of 3‐MDG homopolymerization was 140 ± 3.8 kJ · mol^?1, the polymerization enthalpy was ΔH_MDG = ?51.6 ± 1.9 kJ · mol^?1 and the calculated adiabatic temperature rise was ΔT_ad = 78.5 K. The effects of the initiator and the emulsifier concentrations on the 3‐MDG/BA batch copolymerization kinetics and on the colloidal properties of the final sugar latexes were studied at 60 °C. At higher emulsifier and initiator concentration, respectively, the polymerization rate increases and the particle size decreases, but the trends do not conform to the Smith‐Ewart theory. Polydisperse sugar latex particles with a mean diameter in the range of 50–67 nm were obtained.

Relationship between the activation energy and the conversion for BA (open symbols) and 3‐MDG (solid symbols).     

Ionic liquids as catalytic additives for the acceleration of the photopolymerization of poly(ethylene glycol dimethacrylate)s

BACKGROUND: The fast development of practical applications of photopolymerizable compositions (PPCs) leads to a growing demand for the elaboration of novel monomers and simultaneously for the investigation of three‐dimensional polymerization mechanisms including the possible influence of initiator, additives, etc. The aim of the current study is to explore and clarify the role of ionic liquids (ILs) as environmentally friendly catalytic additives in the photopolymerization of poly(ethylene glycol dimethacrylate)s. RESULTS: The photopolymerization of triethylene glycol dimethacrylate (TEGDM) and poly(ethylene glycol‐400 dimethacrylate) (PEGDM) in the presence of various ILs both imidazolium‐based, i.e. [1‐methyl‐3‐alkylim]⁺ (CF₃SO₂)₂N^? (im = imidazolium; alkyl = C₂H₅, C₄H₉, C₁₄H₂₉), and phosphonium‐based, i.e. [P⁺ (C₆H₁₃)₃(C₁₄H₂₉)]X^? (X^? = PF₆^?, BF₄^?, (CF₃SO₂)₂N^?, Cl^?), as catalytic additives was investigated. The influence of the concentration of the ionic salts as well as the nature of the ILs upon the photopolymerization was studied in detail. It was found that imidazolium ILs accelerate TEGDM photopolymerization and suppress the polymerization of PEGDM. In contrast, polymerization of PEGDM with extra small amounts of phosphonium ionic solvents proceeded at a high rate and offered access to new polymers and the utilization of low‐reactivity monomers in PPCs. CONCLUSION: The most striking advantage is that the use of certain ILs permits the control of polymerization rate to achieve maximum oligomer conversion. Copyright © 2007 Society of Chemical Industry     

Gel Polymer Electrolyte with Anion‐Trapping Boron Moieties via One‐Step Synthesis for Symmetrical Supercapacitors

A novel gel polymer electrolyte (GPE) which is based on new synthesized boron‐containing monomer, benzyl methacrylate, 1 m LiClO₄/N,N‐dimethylformamidel liquid electrolyte solution is prepared through a one‐step synthesis method. The boron‐containing GPE (B‐GPE) not only displays excellent mechanical behavior, favorable thermal stability, but also exhibits an outstanding ionic conductivity of 2.33 mS cm^?1 at room temperature owing to the presence of anion‐trapping boron sites. The lithium ion transference in this gel polymer film at ambient temperature is 0.60. Furthermore, the symmetrical supercapacitor which is fabricated with B‐GPE as electrolyte and reduced graphene oxide as electrode demonstrates a broad potential window of 2.3 V. The specific capacitance of symmetrical B‐GPE supercapacitors retains 90% after 3000 charge–discharge cycles at current density of 1 A g^?1.     

1‐(bromoacetyl)pyrene and its arsonium salt as novel photoinitiators for styrene polymerization

The photopolymerization of styrene (Sty) in DMSO induced by pyrene (Py), 1‐Acetylpyrene (AP), 1‐(Bromoacetyl) pyrene (BP), and 1‐Acetylpyrene triphenyl arsonium bromide (APAS) has been investigated. Under all conditions employed, Py was completely ineffective. Incorporation of a chromophoric (? COCH₃) moiety introduces photoinitiating activity into Py. It was observed that introduction of Br into AP markedly accelerated the rate of UV irradiation‐induced polymerization. BP was further modified to its arsonium salt (APAS). The kinetics and mechanism of polymerization using BP and APAS as initiators have been investigated in detail. The polymerization with BP followed nonideal kinetics (R_p ∝ [BP]^0.8 [Sty]^1.1) with respect to initiator concentration whereas ideal kinetics (R_p ∝ [APAS]^0.48 [Sty]^1.1) was observed when APAS was used as initiator. Degradative transfer is thought to be mainly responsible for this unusual kinetic behavior for BP–Sty system. The kinetic data proved that BP was more effective and faster initiator than APAS. In both the cases, the mechanism of polymerization was free radical as evident by inhibiting the effect of hydroquinone and ESR studies. IR and NMR spectra showed the atactic nature of polystyrene. © 2006 Wiley Periodicals, Inc. J Appl Polym Sci 101: 1793–1798, 2006     

Synthesis and characterization of maleylated cellulose-<Emphasis Type="Italic">g</Emphasis>-polyacrylamide hydrogel using TiO<Subscript>2</Subscript> nanoparticles under sunlight

Graft polymerization onto the cellulose is one way to produce semisynthetic copolymers and semiconductors were hardly used as initiators. Maleylated cellulose (MC) with different degree of carboxyl groups was synthesized and degree of carboxyl groups was determined using titration method. Then the graft copolymers of acrylamide (AM) on MC were synthesized by titanium dioxide semiconductor photoinitiator in aqueous suspension under sunlight. The effect of different parameters, such as the degree of carboxyl groups, degassing of atmosphere, reactor type, light source, MC/AM ratio, and initiator concentration, was evaluated in the synthesis of graft copolymers. MC with a high degree of carboxyl groups about 2.8 mmol g^?1 was selected for graft photopolymerization. Maximum monomer conversion (55%) for Maleylated cellulose-g-polyacrylamide (MC-g-PAM) was achieved with 0.5 mg TiO₂, MC/AM = 0.056, argon atmosphere, sunlight source, and double quartz tube reactor. The maximum amount of equilibrium swelling (41 g g^?1) was achieved for MC-g-PAM with 34% monomer conversion. The resulting graft copolymers were characterized by FT-IR, SEM, and TGA. Synthesis of MC-g-PAM using TiO₂ nanoparticles (NPs) as the initiator was done successfully that shows the TiO₂ NPs are useable in graft polymerization of acrylamide monomers onto the MC under sunlight.     

Kinetics and modeling of the diffusion‐controlled diallyl terephthalate polymerization

Free radical polymerization kinetics of diallyl terephthalate in bulk was investigated in a wide temperature range from 50°C to 150°C with four different peroxide initiators. Conversion points were measured using Fourier Transform Infrared (FTIR) measurements. The initiator efficiencies and the initiator decomposition rate constants were evaluated from special experiments, applying the theory of dead end polymerization. In addition, the ratios between the degradative and the effective kinetic rate constants to propagation rate constants were obtained from molecular weight measurements at various initiator concentrations. The ratio of chemically controlled termination and propagation rate constant k/k_tc of the polymerization system was obtained using the initial rates of polymerization and the number average molecular weight data between 0.25 · 10^?3 and 15.7 · 10^?3 L mol^?1 s^?1. The glass transition temperature of the polymer, 191°C, was measured by the Alternating Differential Scanning Calorimetry (ADSC) technique. Computed conversions from the developed kinetic model were in good agreement with the conversion and molecular weight measured data. The values of diffusion controlled propagation and termination rate constants k_td0 and k_pd0 with clear and physical meaning were the only two parameters obtained from the developed kinetic model fitting. Polym. Eng. Sci. 44:2005–2018, 2004. © 2004 Society of Plastics Engineers.     

Kinetics of azo‐initiated 1‐vinyl‐2‐pyrrolidone polymerizations at low conversions in aqueous media

The free‐radical polymerization behavior of 1‐vinyl,2‐pyrrolidone (NVP) was studied at low conversions, using capillary dilatometry. The aqueous media were kept at neutral pH and the studies were conducted isothermally, at 40 or 45°C. The azo‐type initiators used were 4,4′‐azobis‐4‐cyanopentanoic acid (ACPA), 2,2′‐azobisisobutyronitrile (AZBN), and 2,2′‐azobis[2‐(2‐imidazolin‐2‐yl)propane dihydrochloride] (ABDH). The monomer concentration and initiator concentration ranges were 1.17–2.34 mol L⁻¹ and 1–8 mmol L⁻¹, respectively. The rates of polymerization (R_p) and orders of reaction with respect to NVP and the initiator were evaluated and the kinetic equations were found to be R_p ∝ [NVP] [ACPA]^1.2; R_p ∝ [NVP] [AZBN]^1.1; and R_p ∝ [NVP]^2.2 [ABDH]^1.1. The polymers obtained were characterized by their viscosity numbers and correlation of the viscosity average molecular weights made with the type and amount of the azo initiator. © 2000 John Wiley & Sons, Inc. J Appl Polym Sci 75: 239–246, 2000     

Fe‐mediated ICAR ATRP of styrene and acrylonitrile in polyethylene glycol

In this contribution, random copolymers of p(styrene‐co‐acrylonitrile) via initiators for continuous activator regeneration (ICAR) in atom transfer radical polymerization (ATRP) (ICAR ATRP) of styrene and acrylonitrile (SAN) were synthesized at 90°C in low molecular weight polyethylene glycol (PEG‐400) using CCl₄ as initiator, FeCl₃·6H₂O as catalyst, succinic acid as ligand and thermal radical initiator azobisisobutyronitrile (AIBN) as thermal free radical initiator. In this system, well‐defined copolymer of SAN was achieved. The kinetics results showed that the copolymerization rate obeyed first‐order kinetics model with respect to the monomer concentration, and a linear increase of the molecular weights with the increasing of monomer conversion with narrow molecular weight distribution was observed in the range of 1.1–1.5. The conversion decreased with increasing the amount of FeCl₃·6H₂O and increased with increasing the molar ratio of [St]₀/[AN]₀/[CCl₄]₀ and temperature. AIBN has a profound effect on the polymerization. The activation energy was 55.67 kJ mol^?1. The living character of copolymerization was confirmed by chain extension experiment. The resultant random copolymer was characterized by ¹H‐NMR and GPC. © 2013 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2014 , 131, 40135.     

Electrochemical measurements for studying the polymerization process and critical point behaviors of hydrogels

We propose a new technique based on electrochemical measurements for studying the critical point behaviors of the sol–gel transition of acrylamide–N,N′‐methylene bisacrylamide hydrogels. In this technique, no chemical activator is used for accelerating the polymerization reaction. However, a potential difference is applied by means of silver and calomel electrodes placed in the reaction mixture. The silver electrode begins to be ionized and loses its electrons. The free radicals, ^?O₃S? O^?, H^?, and ^?OH, form on the silver electrode via persulfate dissociation. The polymerization is initiated by means of these free radicals. The current measured during the gelation processes passes through a maximum (a Gaussian‐like behavior) and varies linearly with the reaction time during linear polymerization. All the parameters (the monomer, initiator, and crosslinker concentrations, the applied voltage, and the stirring rate of the reacting mixture) affecting the current have been studied in detail. We show that the maxima appearing in the current–time plots correspond to the gelation thresholds, the so‐called sol–gel transition points. We also analytically prove that the current monitors the weight‐average degree of polymerization (DP_w) and the gel fraction (G) below and above the threshold, respectively. The scaling behaviors of DP_w and G have been tested near the gelation thresholds, and we have observed that the critical exponents γ and β, defined for DP_w and G, agree with the predictions by mean‐field theory. © 2009 Wiley Periodicals, Inc. J Appl Polym Sci, 2009     

Effect of acrylic acid neutralization on ‘livingness’ of poly[styrene‐ran‐(acrylic acid)] macro‐initiators for nitroxide‐mediated polymerization of styrene

BACKGROUND: The effect of acrylic acid neutralization on the degradation of alkoxyamine initiators for nitroxide‐mediated polymerization (NMP) was studied using styrene/acrylic acid and styrene/sodium acrylate random copolymers (20 mol% initial acrylate feed concentration) as macro‐initiators. The random copolymers were re‐initiated with fresh styrene in 1,4‐dioxane at 110 °C at SG1 mediator/BlocBuilder^® unimolecular initiator ratios of 5 and 10 mol%. RESULTS: The value of k_pK (k_p = propagation rate constant, K = equilibrium constant) was not significantly different for styrene/acrylic acid and styrene/sodium acrylate compositions at 110 °C (k_pK = 2.4 × 10^?6–4.6 × 10^?6 s^?1) and agreed closely with that for styrene homopolymerization at the same conditions (k_pK = 2.7 × 10^?6–3.0 × 10^?6 s^?1). All random copolymers had monomodal, narrow molecular weight distributions (polydispersity index M?_w/M?_n = 1.10–1.22) with similar number‐average molecular weights M?_n = 19.3–22.1 kg mol^?1. Re‐initiation of styrene/acrylic acid random copolymers with styrene resulted in block copolymers with broader molecular weight distributions (M?_w/M?_n = 1.37–2.04) compared to chains re‐initiated by styrene/sodium acrylate random copolymers (M?_w/M?_n = 1.33). CONCLUSIONS: Acrylic acid degradation of the alkoxyamines was prevented by neutralization of acrylic acid and allowed more SG1‐terminated chains to re‐initiate the polymerization of a second styrenic block by NMP. Copyright © 2008 Society of Chemical Industry     

Primary amine functionalized polystyrenes by atom transfer radical polymerization

Primary amine functionalized polystyrenes were prepared in quantitative yields by atom transfer radical polymerization using the adduct of 1‐(bromoethyl)benzene with 1‐(4‐aminophenyl)‐1‐phenylethylene as initiator for styrene polymerization in the presence of a copper(I) bromide/N,N,N′,N′,N″‐pentamethyldiethylenetriamine catalyst system. The polymerizations proceeded via a controlled free radical polymerization process to afford quantitative yields of the corresponding primary amine functionalized polystyrenes with predictable molecular weights (M_n = 2 × 10³ to 10 × 10³ g mol^?1), relatively narrow molecular weight distributions (M_w/M_n = 1.03–1.49), well defined chain‐end functionalities and initiator efficiencies as high as 0.92. The polymerization process was monitored by gas chromatographic analysis. The primary amine functionalized polymers were characterized by thin layer chromatography, size exclusion chromatography, potentiometry and spectroscopy. Experimental results are consistent with quantitative functionalization via the 1,1‐diphenylethylene derivative. Polymerization kinetic measurements show that the polymerization reaction follows first order rate kinetics with respect to monomer consumption and the number average molecular weight increases linearly with monomer conversion. © 2003 Society of Chemical Industry     

Amelioration of electrochemical and photovoltaic performances on P(VP‐co‐VAc) based gel polymer electrolyte by incorporating double salt for dye‐sensitized solar cells

Dye‐sensitized solar cell (DSSC) is an alternative photovoltaic application used to replace the liquid electrolyte dependent conventional photovoltaic cell. In this research, gel polymer electrolyte (GPE) was used to replace the unstable liquid electrolyte. This GPE consists of poly[1‐vinylpyrrolidone‐co‐vinyl acetate] (P[VP‐co‐VAc]), tetrabutylammonium iodide (TBAI), sodium iodide (NaI), iodine (I₂), ethylene carbonate (EC), and propylene carbonate (PC). The GPE was tested for its ionic conductivity and an optimum level was reached at sample with 30% TBAI and 6% NaI at 1.17 × 10^?3 S cm^?1. The DSSC was then fabricated with all GPEs and a photovoltaic performance study was conducted. As a result, the highest photovoltaic conversion efficiency (PCE), η for a single salt was 3.04% for 40% TBAI. When a second salt is added, the system showed improvement in efficiency, η to 4.54% with short circuit current density, J_sc of 11.02 mA cm^?2 and open circuit voltage, V_oc of 0.67 V and FF of 61%. The other changes after the addition of TBAI and NaI salts have been observed through X‐ray diffraction, Fourier transformation and thermal analysis studies. © 2016 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2016 , 133, 43805.     

Kinetics and modeling of diethylene glycol bisallyl carbonate bulk polymerization

The free‐radical polymerization kinetics of diethylene glycol bisallyl carbonate in bulk were investigated with Fourier transform infrared and Fourier transform Raman techniques in a wide temperature range of 50–140°C with four different peroxide initiators. In addition, the ratios of the degradative kinetic rate constant to the propagation rate constant under different reaction conditions were obtained from molecular weight measurements under various reaction conditions. The ratio of the chemically controlled termination and propagation rate constants of the polymerization system were obtained with the initial rates of polymerization and the number‐average molecular weight data, which were between 8.22 × 10^?5 and 1.47 × 10^?3 L mol^?1 s^?1. The initiator efficiencies were evaluated with special experiments at low initiator concentrations with the theory of dead‐end polymerization. The computed conversions from the developed kinetic model were in good agreement with the conversion and molecular weight measured data. The values of the diffusion‐controlled propagation and termination rate constants, with clear and physical meaning, were the only two parameters obtained from the developed kinetic model fitting the measured conversion points. © 2005 Wiley Periodicals, Inc. J Appl Polym Sci 96: 345–357, 2005