[Hydroxy(tosyloxy)iodo]benzene as Thermal initiator for the Radical Polymerization of Methyl Methacrylate

Abstract

The thermal polymerization of methyl methacrylate in a solution of N,N-dimethylacetamide has been studied using [hydroxy(tosyloxy)- iodo]benzene (HTIB) as the initiator. The rate of polymerization was a direct function of the monomer and initiator concentrations. The initiator and monomer exponent values expressing this dependence were found to be 1.0 and 0.8, respectively. The overall activation energy of polymerization was estimated to be 45 kJ·mol^?-1. The polymerization was inhibited in the presence of hydroquinone. The effect of various solvents on the polymerization rate was studied. The polymer prepared with HTIB (0.47 × 10^?3 mol·L^?-1) had a number-average molecular weight of 138,000 and a glass transition temperature of 106°C. The polymer showed good thermal stability as determined by thermogravimetric analysis.     

Characteristics of proton conducting polymer electrolyte based on chitosan acetate complexed with CH3COONH4

The polymer electrolytes based on chitosan and ammonium acetate (CH₃COONH₄) were prepared by solution casting technique and the properties were studied. With the addition of CH₃COONH₄, the amorphous nature of the polymer electrolytes was promoted. The glass transition temperature, activation energy, and conductivity are closely related. Lower the glass transition temperature, lower the activation energy, higher the conductivity. The 40 wt % ammonium acetate doped polymer electrolyte has the lowest glass transition temperature of 369 K, the lowest activation energy of 0.19 eV, and the highest ionic conductivity of 2.87 × 10^?4 S cm^?1 at room temperature. © 2009 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 47: 549–554, 2009     

Synthesis and characterization of poly(benzodithiophene) derivative for organic thin film transistors

Poly{2,6‐bis(3‐dodecylthiophen‐2‐yl) benzo[1,2‐b;4,5‐b′]dithiophene} (PTBT) was synthesized, via oxidative polymerization by oxidative agent (FeCl₃). The mole ratio of FeCl₃ and monomer (3.5:1), and keeping low temperature during the dropping of diluted catalyst were very important for the polymerization without crosslinking. The PTBT was confirmed by ¹H NMR, FTIR spectra, and elemental analysis. The PTBT has very good solubility in organic solvents such as chloroform, tetrahydrofuran, etc, and good thermal stability with T_g of 164 °C. The PTBT shows UV‐optical absorption at 406 nm and photoluminescence (PL) spectroscopy at 504 nm in a film. The highest occupied molecular orbital (HOMO) energy of the polymer is ?5.71 eV by measuring cyclic voltammetry (CV). A solution‐processed polymer thin film transistor device shows a mobility of 3 × 10^?5 – 8 × 10^?5 cm² V^?1 s^?1, and an on/off current ratio of 10⁴. © 2007 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 45: 5277–5284, 2007     

The Effect of Active Carbon on the Kinetics of Polymerization of Methyl Methacrylate

Rates of 2–2¹?azobisisobutyronitrile initiated polymerization of methyl methacrylate in benzene were determined at 77.2, 65.0, and 50.0°C. The variation of molecular weight of the polymer with temperature and conversion was also studied. At a fixed conversion of 2.0%, the molecular weight decreased from 2.05 × 10⁵ at 50°C to 1.4 × 10⁵ at 77.2°C. The ratio of the propagation rate coefficient to the square root of the termination rate coefficient was found to be 0.61, 0.397, and 0.374 at 77.2, 65.0, and 50.0°C, respectively, with an uncertainty of ±0.5°C in temperature. The effect of active carbon on the rates of polymerization at 77.2°C was measured. Rates of polymerization decreased in the presence of active carbon. For example, the initial rate of polymerization decreased from 7.8 × 10^?4 mole/(liter min) to 4.6 × 10^?4 mole/(liter min) when the carbon concentration was varied from 0 to 9.65 g/liter. The molecular weight of the polymer increased from an average of 1.4 × 10⁵ in the absence of carbon to 1.5 × 10⁵ when carbon was present.     

Evaluation of nonlinear optical susceptibility of polydiacetylenes by third harmonic generation

Nonlinear optical susceptibility χ⁽³⁾ of polydiacetylenes has been evaluated by third harmonic generation. First, in order to obtain the χ⁽³⁾ tensor component along the polymer main chain, thin single crystals of two representative polydiacetylenes, poly-PTS and poly-DCHD were made by utilization of sampling technique in microscopy, i.e., the microtome cutting of single crystal embedded in plastic resin. The THG intensity observed was proportional to cos⁸θ, where θ was the angle between the polymer main chain and the polarization of laser light. The χ⁽³⁾ value of poly-DCHD was found to be rather higher than that of poly-PTS. At resonant wavelength of 1.97 μm, the χ⁽³⁾ of poly-DCHD attained 8 x 10^?10 esu. Furthermore, it was confirmed that when geometrical correction were properly made, the χ⁽³⁾ obtained from polycrystalline thin film of poly-PTS agreed well with that from thin single crystals. Secondary, regarding poly-diphenyldiacetylene derivatives, it was found that the π-conjugation between the polymer main chain and aromatic substituents was effective on the improvement of χ⁽³⁾ values. The χ⁽³⁾ magnitudes of poly-BTFP and poly-DFMP reflect well the dihedral angles between polymer main chain and the phenyl substituents (58° for poly-BTFP and 67° for poly-DFMP) as a measure of π-conjugation. Especially, at nonresonant region of 2.1 μm the χ⁽³⁾ of poly-BTFP is about 5 times greater than that of poly-PTS.     

Synthesis and characterization of a thiadiazole/benzoimidazole‐based copolymer for solar cell applications

In this study, we synthesized a new polymer, PCTDBI , containing alternating carbazole and thiadiazole‐benzoimidazole (TDBI) units. This polymer (number‐average molecular weight = 25,600 g mol^?1), which features a planar imidazole structure into the polymeric main chain, possesses reasonably good thermal properties (T_g = 105 °C; T_d = 396 °C) and an optical band gap of 1.75 eV that matches the maximum photon flux of sunlight. Electrochemical measurements revealed an appropriate energy band offset between the polymer's lowest unoccupied molecular orbital and that of PCBM, thereby allowing efficient electron transfer between the two species. A solar cell device incorporating PCTDBI and PCBM at a blend ratio of 1:2 (w/w) exhibited a power conversion efficiency of 1.20%; the corresponding device incorporating PCTDBI and PC₇₁BM (1:2, w/w) exhibited a PCE of 1.84%. © 2010 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem, 2010     

Some studies on a polymer from urea

A polymer having the structure of guanidinopolyhydroxynitrile has been produced by heating an equimolar mixture of urea and anhydrous ZnCl₂ in nitrogen at 300°C and 27 atm. The structure has been established from elemental analysis, percentage of nitrogen as primary amine, and ultraviolet and infrared spectra of the polymer and its derivatives. A mechanism of the polymerization based on some experimental evidence has been suggested. Its physical properties have been attributed to its skeletal structure and ring closure by hydrogen bonding. Thermograms reveal that it is stable to 150°C, after which it decomposes slowly till a 75% weight residue is obtained at 575°C with a constant weight plateau extended to 680°C. In acid solvents, protonation occurs at the ? NH₂ group or the azomethine nitrogen atoms, producing polycations. The polyelectrolytic character in acids has been confirmed by viscometric and osmotic studies and the molecules tend to be both coiled up and associated in solutions. [n] in anhydrous formic acid is 0.3636 dl/g. The molecular weights of the polymer and its various fractions range between 39,500 and 25,900. Dielectric constants, dielectric losses, and conductivities of the polymer have also been measured as functions of frequency and temperature and it has been proved that the dispersion is due to dipole polarization. The average energy of the dipole is 1.73 × 10^?2 eV/°K, the intrinsic activation energy for conduction is 0.186 eV, the conductivities being of the order of 2 × 10^?6 to 7 × 10^?7 mho-cm^?1. The polymer is therefore a semiconductor. The number of charge carriers is 2.12 × 10¹⁶/cm², which agrees reasonably well with the value, 6.66 × 10¹⁶, obtained from spin-density calculations from ESR signals.     

Radical polymerization of methyl methacrylate in the presence of stereoregular poly(methyl methacrylate). V. Kinetics of initial template polymerization

The influence of stereoregular poly(methyl methacrylate) (PMMA) as a polymer matrix on the initial rate of radical polymerization of methyl methacrylate (MMA) has been measured between ?11 and +60°C using a dilatometric technique. Under proper conditions an increase in the relative initial rate of template polymerization with respect to a blank polymerization was observed. Viscometric studies showed that the observed effect could be related to the extent of complex formation between the polymer matrix and the growing chain radical. The initial rate was dependent on tacticity and molecular weight of the matrix polymer, solvent type and polymerization temperature. The accelerating effect was most pronounced (a fivefold increase in rate) at the lowest polymerization temperature with the highest molecular weight isotactic PMMA as a matrix in a solvent like dimethylformamide (DMF), which is known to be a good medium for complex formation between isotactic and syndiotactic PMMA. The acceleration of the polymerization below 25°C appeared to be accompanied by a large decrease in the overall energy and entropy of activation. It is suggested that the observed template effects are mainly due to the stereoselection in the propagation step (lower activation entropy Δ S_p^?) and the hindrance of segmental diffusion in the termination step (higher activation energy Δ E_t^?) of complexed growing chain radicals.     

Radiation-induced ionic polymerization of isobutyl vinyl ether in bulk

The radiation-induced ionic polymerization of isobutyl vinyl ether was investigated under conditions where the monomer was dried with molecular sieves. The investigation covered the temperature range from ?16°C to 90°C, and the dose-rate range from 10¹⁵ to 10²⁰ eV/g-sec, using both γ-rays and electrons. A very high overall activation energy of 15.9 kcal/mole was found for the process below 30°C. Above 30°C, however, the value of the overall activation energy dropped to 4.9 kcal/mole, a phenomenon which is ascribed to the solvation of the propagating carbonium ion below 30°C. The dose-rate dependence of the rate of polymerization was found to be 0.58 over the entire dose-rate range investigated. The molecular weight of the polymer was found to be far less sensitive to trace amounts of water than the rate of polymerization. The molecular weight of the polymer depended strongly on the irradiation temperature, reaching a maximum value of about 120,000 at 35°C. It is shown that at temperatures above 20°C regenerative chain transfer processes play an important role in determining the molecular weight of the polymer.     

Synthesis and properties of triaryl diamine‐based hole‐transporting monomer and polymer

The synthesis and properties of hole‐transporting triaryl diamine‐based low‐molar‐mass compounds and polymer are reported. Comparative study on their thermal, optical, and photoelectrical properties is presented. All the synthesized compounds are found to form glasses with the glass transition temperatures in the range of 43–119 °C as characterized by differential scanning calorimetry. The ionization potentials of these compounds range from 5.31 to 5.40 eV as determined by electron photoemission method. Hole‐drift mobilities in the films of the synthesized compounds were estimated by the xerographic time‐of‐flight technique. They were found to reach 10^?3 cm²/Vs at electric field of 6.4 × 10⁵ V/cm. © 2008 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 46: 4674–4680, 2008     

Molecular design,synthesis, and nonlinear optical properties of novel T‐type polyimides with exceptionally high thermal stability of the second harmonic generation

2,5‐Bis‐(3,4‐dicarboxyphenylcarboxyethoxy)‐4′‐nitrostilbene dianhydride was prepared and reacted with 1,4‐phenylenediamine, 4,4′‐oxydianiline, 4,4′‐diaminobenzanilide, and 4,4′‐(hexafluoroisopropylidene)dianiline to yield unprecedented novel T‐type polyimides ( 4 – 7 ) containing 2,5‐dioxynitrostilbenyl groups as nonlinear optical chromophores, which constituted parts of the polymer backbones. 4 – 7 were soluble in polar solvents such as acetone and N,N‐dimethylformamide. They showed thermal stability up to 300 °C in thermogravimetric analysis thermograms; the glass‐transition temperatures obtained from differential scanning calorimetry thermograms were around 153 °C. The second harmonic generation (SHG) coefficients (d₃₃) of poled polymer films at the 1064‐cm^?1 fundamental wavelength were around 4.35 × 10^?9 esu. The dipole alignment exhibited exceptionally high thermal stability even at 45 °C higher than the glass‐transition temperature, and there was no SHG decay below 200 °C because of the partial main‐chain character of the polymer structure, which was acceptable for nonlinear optical device applications. © 2004 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 42: 3189–3199, 2004     

Precipitation polymerization of acrylamide using vazo-33 as an initiator and acetonitrile/water mixtures as the solvent

Precipitation polymerization of acrylamide initiated by a thermal initiator, Vazo-33 (DuPont Vazo Initiator), was achieved at a solvent composition of acetonitrile/water = 4/6 (vol/vol). The polymerization kinetics were investigated in the acrylamide [M] concentration range 0.86–2.27M, Vazo-33 [I] concentration range 1.4–11.0 × 10^?4M, and temperature range 30–40°C. Polymerization was carried out in reaction ampules and the rate was determined gravimetrically. Number-average molecular weight was obtained from intrinsic viscosity. The precipitation polymerization rate varied as [M]^2.16 and [I]^0.44. Number-average molecular weight was proportional to [M]^1.22 and inversely proportional to [I]^0.31. The overall reaction activation energy was calculated as 17.3 kcal/mol in the temperature range studied. The optimal reaction conditions studied were: acetonitrile/water = 4/6, temperature = 40°C, [M] = 1.95M and [I] = 2.8 × 10^?4M. One hundred percent conversion was achieved in 90 min and a polymer with a number-average molecular weight of 1,200,000 was obtained.     

Polymerization of methyl methacrylate by 2‐pyrrolidinone and n‐dodecyl mercaptan

The bulk polymerization of methyl methacrylate initiated with 2‐pyrrolidinone and n‐dodecyl mercaptan (R‐SH) has been explored. This polymerization system showed “living” characteristics; for example, the molecular weight of the resulting polymers increased with reaction time by gel permeation chromatographic analysis. Also, the polymer was characterized by Fourier transform infrared spectroscopy, ¹H NMR, and ¹³C NMR techniques. The polymer end with the iniferter structures was found. By the initial‐rate method, the polymerization rate depended on [2‐pyrrolidinone]^1.0 and [R‐SH]⁰. Combining the structure analysis and the polymerization‐rate expression, a possible mechanism was proposed. n‐Dodecyl mercaptan served dual roles—as a catalyst at low conversion and as a chain‐transfer agent at high conversion. Finally, the thermal properties were studied, and the glass‐transition temperature and thermal‐degradation temperature were, respectively, 25 and 80–100 °C higher than that of the azobisisobutyronitrile system. © 2002 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 40: 3692–3702, 2002     

Photoinitiated polymerization of methacrylates comprising phenyl moieties

Investigation of photopolymerization kinetics of 4-(4-methacryloyloxyphenyl)-butan-2-one (1) in comparison with 2-phenoxyethyl methacrylate (2) and phenyl methacrylate (3) using a UV-LED emitting at 395 nm shows significantly faster polymerization of 1 compared to both 2 and 3 at 40°C. Vitrification affects photopolymerization kinetics of all methacrylates under investigation. Interestingly, quantitative final conversion is observed during photoinitiated polymerization of 1 and 2 whereas 3 shows limited conversion at about 80%. Furthermore, higher degree of polymerization is obtained by photoinitiated polymerization of 1 compared to 2 and 3. This shows that the 3-oxobutyl substituent at the phenyl ring of 1 significantly affects both polymerization kinetics and final conversion of the photoinitiated polymerization. Moreover, an additional higher molecular weight fraction is observed in case of polymerization of 1 at 85°C that is above the glass transition temperature of the polymer formed during photoinitiated polymerization. As a thermal polymerization at 85°C in the absence of light results in a high molecular weight polymer as well, an additional thermal process may be discussed as reason for the higher molecular weight polymer fraction in case of the photopolymer made at 85°C.     

Synthesis and nonlinear optical properties of novel Y‐type polyester containing tricyanovinylthiazolylazoresorcinoxy group with enhanced thermal stability of dipole alignment

Novel Y‐type polyester 4 containing 5‐methyl‐4‐{5‐(1,2,2‐tricyanovinyl)‐2‐thiazolylazo}resorcinoxy groups as nonlinear optical (NLO) chromophores, which are parts of the polymer backbone, was prepared, and its NLO properties were investigated. Polyester 4 is soluble in common organic solvents such as N,N‐dimethylformamide and dimethylsulfoxide. Polymer 4 shows a thermal stability up to 250 °C from thermogravimetric analysis with glass‐transition temperature obtained from differential scanning calorimetry of approximately 94 °C. The second harmonic generation (SHG) coefficient (d₃₃) of poled polymer film at 1560‐nm fundamental wavelength is 8.12 × 10^?9 esu. The dipole alignment exhibits a thermal stability even at 6 °C higher than glass‐transition temperature (T_g), and no significant SHG decay is observed below 100 °C due to the partial main‐chain character of polymer structure, which is acceptable for NLO device applications. © 2011 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem, 2011     

Phosphorescence studies of relaxation effects in bulk polymers. I. Depolarization measurements of segmental relaxation in poly(methyl acrylate)

This paper reports the first measurements of macromolecular segmental relaxation times by phosphorescence depolarization. Steady-state phosphorescence polarization experiments were performed on samples of poly(methyl acrylate) incorporating 0.5 wt % copolymerized acenaphthylene or 1-vinyl naphthalene as phosphorescent probes over the temperature range 77 to 310°K. Depolarization of phosphorescence occurs with the onset of segmental motion of the polymer at ca. 278°K. Motion of either probe is characterized by an activation energy of 195 (±5) kJ mole^?1, which is in fair agreement with the mean value of 230 kJ mole^?1 estimated for the segmental relaxation of poly(methyl acrylate) by dielectric and mechanical relaxation techniques. Transient depolarization measurements confirm the absence of probe motion below the glass transition temperature. Phosphorescence intensity and triplet state lifetime data are capable of detection of a second transition in the polymer in accord with observations using more conventional techniques.     

The thermal polymerization of styrene in diethyladipate at temperatures up to 160°

The thermal polymerization of styrene in diethyladipate has been studied dilatometrically at temperatures from 90 to 160°. The rate was found to be directly proportional to (monomer concentration)² and the molecular weight of the polymer formed was controlled mainly by chain transfer to monomer, particularly at the higher temperatures. A value of 86 ± 2 kJ/mol was obtained for the overall energy of activation for the polymerization, and values of 7.16 × 10^?5. 2.0 × 10^?4 and 5.5 × 10^?4 were found for the transfer constant for diethyladipate at 120. 140 and 160° respectively.     

Anthracene‐thieno[3,4‐c]pyrrole‐4,6‐dione based donor–acceptor conjugated copolymers for applications in optoelectronic devices

Three novel alternating copolymers of thieno[3,4‐c]pyrrole‐4,6‐dione (TPD) and triisopropylsilylacetylene‐functionalized anthracene were prepared via Suzuki polymerization. Various solubilizing substituents were attached to the TPD moiety in order to ascertain the impact they have upon the optical, electrochemical, and thermal properties of the resulting polymers. All copolymers showed good solubility and thermal stability with decomposition temperatures in excess of 300°C. Optical properties revealed that PTATPD(O), PTATPD(DMO), and PTATPD(BP) displayed optical energy gaps in excess of 2.0 eV. It is speculated that steric repulsion between solubilizing groups on repeat units along polymer chains reduces their planarity and decreases their electronic conjugation. The amorphous nature of the polymers was confirmed with differential scanning calorimetry and powder X‐ray diffraction. The highest occupied molecular orbital levels of the three polymers are unaffected by the different solubilizing chains. However, they exert some influence over the lowest unoccupied molecular orbital (LUMO) levels with PTATPD(BP) and PTATPD(O) displaying the lowest LUMO levels (?3.4 eV). In contrast, PTATPD(DMO) displayed the highest LUMO level (?3.3 eV). © 2015 The Authors. Polymers for Advanced Technologies Published by John Wiley & Sons Ltd.     

Optical properties of a polydiacetylene crystal: poly-[1,6-di(N-carbazolyl)-2,4-hexadiyne]

Normal incidence reflection spectra and Kramers-Kronig transforms are reported for a polydiacetylene crystal, DCHD (substituent group: N-carbazolymethyl). The lowest energy optical transition for the polymer backbone is found at 15 300 cm^?1, the lowest value obtained thus far for a polydiacetylene. The polymer chain and the carbazolyl substituent group may be treated as isolated chromophores - the former dominating the visible portion of the spectra and the latter dominating the UV portion. Polarization studies for the (001) and (10$\text{1}\text{?}$) faces of DCHD permit unambiguous assignment of the two lowest energy transitions in the carbazolyl group at 28 750 cm^?1 and 33 250 cm^?1 as short- and long-axis polarized, respectively.     

Aqueous polymerization of acrylamide

The polymerization of acrylamide (I) initiated by a potassium bromate—thioglycollic acid (TGA) redox pair has been studied in aqueous media at 30°C in a nitrogen atmosphere. The reaction order related to the catalyst concentration (KBrO₃) was 0.501, which indicated a bimolecular mechanism for the termination reaction in the range of 1.0?3.0 × 10^?3 mole/liter. The polymerization rate varied linearly with monomer (I) concentration over the range of 1.0?5.0 × 10^?2 mole/liter. A typical behavior is observed, however, by changing the thioglycollic acid concentration. The initial rate of polymerization (Ri), as well as the maximum conversion, increases by increasing the temperature to 30°C, but the initial rate and the maximum conversion falls as the temperature rises above 30°C. The overall energy of activation is 6.218 kcal in the temperature range of 20–40°C. Water-miscible organic solvents, namely, CH₃OH and C₂H₅OH, depress the rate of polymerization.