Curcumin,A Novel Natural Photoinitiator for the Copolymerization of Styrene and Methylmethacrylate

Curcumin (Cur), a natural colorant found in the roots of the Turmeric plant, has been reported for the first time as photoinitiator for the copolymerization of styrene (Sty) and methylmethacrylate (MMA). The kinetic data, inhibiting effect of benzoquinone and ESR studies indicate that the polymerization proceeds via a free radical mechanism. The system follows ideal kinetics (R_p α[Cur]^0.5[Sty]^0.97[MMA]¹). The reactivity ratios calculated by using the Finemann–Ross and Kelen‐Tudos models were r₁(MMA)=0.46 and r₂(Sty)=0.52. IR and NMR analysis confirmed the structure of the copolymer. NMR spectrum showing methoxy protons as three distinct groups of resonance between 2.2–3.75 δ and phenyl protons of styrene at 6.8–7.1 δ confirmed the random nature of the copolymer. The mechanism for formation of radicals and random copolymer of styrene and MMA [Sty‐co‐MMA] is also discussed.     

1-(Bromoacetyl)pyrene,a novel photoinitiator for the copolymerization of styrene and acrylonitrile

A comparative study on photoinitiated solution copolymerization of Styrene (Sty), with acrylonitrile (AN) using pyrene, 1-acetylpyrene, and 1-(bromoacetyl)pyrene (BrPy) as initiators, showed that the introduction of a chromophoric moiety, bromoacetyl (–COCH₂Br), significantly increased the photoinitiating ability of pyrene. The kinetics and mechanism of copolymerization of Sty with AN (Sty–co–AN) using BrPy as photoinitiator has been studied in detail. The kinetic data, inhibiting effect of benzoquinone, and electron spin resonance (ESR) studies suggest that the polymerization proceeds via a free radical mechanism. The system followed non-ideal kinetics (R _p α[BrPy]^0.7[Sty]^1.09[AN]^1.01) and degradative solvent transfer reasonably explained these kinetic non-idealities. The co-monomer reactivity ratios calculated by using the Finemann–Ross and Kelen–Tudos models were r ₁ (Sty) = 0.39 and r ₂ (AN) = 0.05. The reactivity ratios strongly indicate that the two monomers enter in almost alternating arrangement along the copolymer chain.     

Synthesis and characterization of amphiphilic and hydrophobic ABA-type tri-block copolymers using telechelic polyurethane as atom transfer radical polymerization macroinitiator

Atom transfer radical polymerization of 2-(dimethylamino) ethylmethacrylate and styrene was carried out using tertiary bromine-terminated telechelic polyurethane as a macroinitiator. The resulting ABA-type amphiphilic, poly (2-(dimethylamino) ethylmethacrylate)-b-polyurethane-b-poly (2-(dimethylamino) ethylmethacrylate) and hydrophobic, polystyrene-b-polyurethane-b-polystyrene tri-block copolymers were characterized by spectral, thermal, and chromatographic techniques. As the conversion increases, [`(M)]<sub>\textn</sub> {\overline M_{_{\text{n}}}} also increases linearly. Theoretical M <sub>n</sub> values of the tri-block copolymers were comparable with the experimental [`(M)]_\textn {\overline M_{_{\text{n}}}} values. These results show that the polymerization of styrene and 2-(dimethylamino) ethylmethacrylate occurred through controlled radical polymerization mechanism. Mole percentage of polystyrene and poly (2-(dimethylamino) ethylmethacrylate) blocks in the tri-block copolymers was calculated using proton nuclear magnetic resonance spectroscopy, and the results were comparable with the gel permeation chromatography results. The glass transition temperatures of polystyrene and poly (2-(dimethylamino) ethylmethacrylate) blocks in the tri-block copolymers appeared at 72 °C and 110 °C, respectively. These results confirm the presence of two phases in the tri-block copolymers.     

Synthesis and characterization of poly(styrene/α-t-butoxy-ω-vinylbenzyl-polyglycidol) microspheres

Polystyrene microspheres with polyglycidol (polyGL) in a surface layer were synthesized in batch radical emulsifier-free emulsion copolymerizations of styrene and surfmers, α-t-butoxy-ω-vinylbenzyl-polyGL macromonomers (VB-polyGL). Macromonomers with number-average molecular weight Mˉ _n=950 (VB-polyGL950) and Mˉ _n=2700 (VB-polyGL2700) were used for these polymerizations. In all syntheses the initial concentrations of styrene and initiator (K₂S₂O₈) were constant. The initial macromonomer-to-styrene ratios were varied from 1.10 × 10⁻³ to 1.64 × 10⁻² mol/mol and from 3.46 × 10⁻⁴ to 3.47 × 10⁻³ mol/mol for VB-polyGL950 and VB-polyGL2700, respectively. The diameters of microspheres obtained were smaller for the syntheses with higher concentrations of macromonomers. Syntheses with VB-polyGL950 yielded microspheres with number-average diameters (Dˉ _n) from 216 to 900 nm and with a bimodal diameter distribution. The number-average diameters of microspheres obtained with VB-polyGL2700 varied from 220 to 650 nm, depending on the initial concentration of macromonomer. Their diameter distributions were monomodal, with a diameter polydispersity parameter (ratio of weight-average and number-average diameters) in the range 1.007≤Dˉ _w/Dˉ _n≤1.022. For each type of microsphere the fraction of polyGL in a surface layer and the surface concentration of sulfate anions were determined. The fraction of polyGL in the surface layer was related to the initial monomer composition in the polymerizing mixture. Adsorption of human serum albumin onto surfaces of some poly(styrene/VB-polyGL) microspheres was up to 10 times lower than for the polystyrene microspheres obtained in a similar emulsifier-free emulsion polymerization of styrene. Received: 26 September 2000/Accepted: 19 February 2001     

Monodisperse micron-sized crosslinked polystyrene particles. IV. Effect of network structure on polymerization procedure

Monodisperse micron-sized polystyrene particles crosslinked using urethane acrylate were produced by dispersion polymerization in ethanol solution and the effect of the crosslinked network structure on the polymerization procedure was studied. The influences of the concentrations of the initiator and urethane acrylate on the particle diameter (D _n), the particle number density (N _p), and the polymerization rate (R _p) were found to obey the approximate relationships D _n ∝ [initiator]^0.43 [urethane acrylate]^0.05, N _p ∝ [initiator]^−1.30 [urethane acrylate]^0.19, and R _p ∝ [initiator]^{0.24 ± 0.02}. The power-law dependence of D _n and N _p on the initiator concentration showed a similar trend to that of linear polystyrene reported in the literature. Especially, it was found that urethane acrylate does not have a serious effect on D _n and N _p of the particles produced. The dependence of R _p on the initiator concentration was observed to be higher than that of linear polystyrene, suggesting that there is still competition between heterogeneous polymerization and solution polymerization because of the crosslinked network structure of the primary particle. Received: 1 April 1999 Accepted in revised form: 29 June 1999     

Agitation requirement for synthesis of micron-sized monodisperse polymer particles in soap-free polymerization method

Single-stage polymerization recently proposed for producing micron-sized polymer particles in aqueous media by Gu, Inukai and Konno (2002) was carried out under the control of agitation with styrene monomer, an amphoteric initiator, 2,2′-azobis [N-(2-carboxyethyl)-2-methylpropionamidine] tetrahydrate and a pH buffer NH₃/NH₄Cl at a monomer concentration of 1.1 kmol/m³ H₂O, an initiator concentration of 10 mol/m³ H₂O and a buffer concentration of [NH₃] = [NH₄Cl] = 10 mol/m³ H₂O. In the polymerizations, impeller speed was ranged from 300 to 500 rpm to satisfy complete dispersion of the monomer phase and not to introduce the gas phase from the free surface. Polymerization experiments under steady agitation indicated that impeller speed was an important factor for size distribution of polymer particles. An increase in impeller speed promoted particle coagulation during the polymerization to enlarge the average size of polymer particles but widen the size distribution. To produce polymer particles with narrow size distribution, stepwise reduction in impeller speed was examined in the polymerization experiments. It was demonstrated that this method was more effective than the steady agitation. The impeller speed reduction could produce highly monodisperse particles with an average size of 2 μm and a coefficient of variation of size distributions of 2.2% that was much smaller than typical monodispersity criterion of 10%.     

May Trifluoromethylation and Polymerization of Styrene Occur from a Perfluorinated Persistent Radical (PPFR)?

The radical polymerization of styrene (St) initiated by a trifluoromethyl radical generated from a perfluorinated highly branched persistent radical (PPFR) is presented with an isolated yield above 70 %. The release of ^.CF₃ radical occurred from a temperature above 85 °C. Deeper ¹H and ¹⁹F NMR spectroscopies of the resulting fluorinated polystyrenes (CF₃-PSts) evidenced the presence of both CF₃ end-group of the PSt chain and the trifluoromethylation of the phenyl ring (in meta-position mainly). [PPFR]₀/[St]₀ initial molar ratios of 3:1, 3:10 and 3:100 led to various molar masses ranging from 1750 to 5400 g mol⁻¹ in 70–86 % yields. MALDI-TOF spectrometry of such CF₃-PSts highlighted polymeric distributions which evidenced differences between m/z fragments of 104 and 172 corresponding to styrene and trifluoromethyl styrene units, respectively. Such CF₃-PSt polymers were also compared to conventional PSts produced from the radical polymerization of St initiated by a peroxydicarbonate initiator. A mechanism of the polymerization is presented showing the formation of a trifluoromethyl styrene first, followed by its radical (co)polymerization with styrene. The thermal properties (thermal stability and glass transition temperature, T_g) of these polymers were also compared and revealed a much better thermal stability of the CF₃-PSt (10 % weight loss at 356–376 °C) and a T_g of around 70 °C.     

Microemulsion polymerization of styrene using a polymerizable nonionic surfactant and a cationic surfactant

High polymer/surfactant weight ratios (up to about 15:1) of polystyrene microlatexes have been successfully produced by microemulsion polymerization using a small amount of polymerizable surfactant, ω-methoxypoly(ethylene oxide)₄₀ undecyl α-methacrylate macromonomer (PEO-R-MA-40), and cetyltrimethylammonium bromide (CTAB). After generating “seeding particles” in a ternary microemulsion containing only 0.2 wt% CTAB and 0.1 wt% styrene, the additional styrene containing less than 1 wt% PEO-R-MA-40 was added dropwise to the polymerized microemulsion for a period of about 4 h at room temperature. PEO-R-MA-40 copolymerized readily with styrene. The stable microlatexes were bluish-transparent at a lower polymer content and became bluish-opaque at a higher polymer content. Nearly monodisperse latex particles with diameters ranging from 50 to 80 nm and their molar masses ranging from 0.6 to 1.6 × 10⁶ g/mol could be obtained by varying the polymerization conditions. The dependence of the number of particles per milliliter of microlatex, the latex particle size and the copolymer molar mass on the polymerization time is discussed in conjunction with the effect of the macromonomer concentration. Received: 25 October/2000 Accepted: 2 February 2001     

The micellization of the diblock copolymer of ethylene oxide and styrene in benzene and the effect on the preparation of the star ABC triblock copolymer of ethylene oxide, styrene and methyl methacrylate

In the preparation of the ABC star triblock copolymer of ethylene oxide, styrene and methyl methacrylate (MMA), the photo-induced charge-transfer complex (CTC) was used to initiate the polymerization of the third monomer MMA. The CTC was composed of the diblock copolymer of poly(ethylene oxide) (PEO) and polystyrene (PS), PEO-b _i -PS, with an aromatic imino group at the conjunction point and benzophenone (BP). It was confirmed that the kinetic behavior of this macromolecular initiation system is nearly the same with a general small radical initiator: the polymerization rate R _p ∝ [PEO-b _i -PS]^0.48[BP]^0.45[MMA]^0.97. Moreover, if the molecular weight of the PEO block is fixed, R _p is independent of the molecular weight of the PS block.  By means of measurements of viscosity and fluorescence, it was found that the micelles of the diblock copolymer PEO-b _i -PS were formed in benzene. The aromatic imino groups were located on the boundary surfaces of the micelles and were fully exposed, and so the BP and MMA molecules easily approached them and affected the charge-transfer polymerization of MMA. Received: 18 August 1998 Accepted in revised form: 25 November 1998     

Synthesis of polystyrene with high melting temperature through BDE/CuCl catalyzed polymerization

No matter what the polymerization manner was, polystyrene with unique highT _m (T _m = 170–285°C) was obtained through polymerization of styrene if the amount of BDE/CuCl catalyst was highly increased (mol ratio: St:CuCl = 25:1-2.5:1). Partial crystallinity of the PSt was observed by characterizations of X-ray diffraction and DSC. Spectra of¹H-NMR and¹³C-NMR showed that syndiotactic structure contained in the obtained PSt was 5% more than that in aPSt (atactic polystyrene). According to the proposed “coordinated radical cage” mechanism, the coordinated state between radical and catalyst center metal Cu should be more closely packed with increasing the BDE/CuCl catalyst amount, which was induced to partial stereospecific polymerization in the coordinated radical polymerization of St.     

Effect of cobalt(III) 1-nitroso-2-naphtholate on free-radical polymerization to vinyl monomers

It has been shown that, at 70°C, cobalt(III) 1-nitroso-2-naphtholate inhibits the free-radical polymerization of styrene, methyl methacrylate, butyl methacrylate, and butyl acrylate. The induction period linearly increases with complex concentration. The polymerization of styrene (120°C) carried out in the presence of cobalt(III) 1-nitroso-2-naphtholate shows typical features of pseudoliving polymerization, namely, linear ln[M]₀/[M]-time and molecular mass-conversion plots. When the monomers are allowed to stand with a complex (7 × 10^?3 mol/l) and an initiator (5 × 10^?3 mol/l) for 1 day at 20°C, the ESR signal corresponding to the nitroxide radical appears. In the course of polymerization, the signal disappears, indicating the consecutive transformation of the cobalt(III) 1-nitroso-2-naphtholate radical into the macronitroxide adduct. Polystyrene samples isolated at various conversions initiate the secondary polymerization of styrene and its block copolymerization with methyl methacrylate.     

Langmuir–Blodgett film of tetraoxocalix[2]arene[2]triazine modified electrode for voltammetric determination of copper ion

In the present work, a new voltammetric sensor, Langmuir–Blodgett (LB) film of tetraoxocalix[2]arene[2]triazine (TOCT) modified glassy carbon electrode (LB_TOCT-GCE), for trace analysis of copper ion in water samples, was prepared. The morphology of LB_TOCT-GCE was characterized by cyclic voltammetric method, electrochemical impedance spectroscopy, and atomic force microscope. The recognizing mechanism of LB_TOCT-GCE for copper ion in aqueous solution was discussed. Under the optimum experimental conditions, using square wave stripping voltammetry and accumulation time of 300 s, the peak currents were linear relationship with Cu²⁺ concentrations in the range of 2 × 10⁻⁹ to 1 × 10⁻⁶ mol L⁻¹, with detection limit of 1 × 10⁻¹⁰ mol L⁻¹. By this method, real samples (lake water, drinking water, and city wastewater) were analyzed with satisfactory results. In addition, the fabricated electrode exhibited a distinct advantage of simple preparation, non-toxicity, good reproducibility, and stability.     

Photopolymerisation of styrene initiated by triphenyl bismuthonium ylide

Photopolymerization of styrene initiated by tetraphenyl cyclopentadiene triphenyl bismuthonium ylide in dioxane was carried out in the presence of visible light (440 nm) at 30 ± 0.2°C for 55 h. The polymerization was inhibited by the presence of hydroquinone which is an evidence of the fact that polymerization takes place by radical mechanism. The system follows ideal radical kinetics (R_p ∝︁ [I]^0.5 [M]). The values of average degree of polymerization (P_n) decreases with the ylide. The mechanism of the reaction was elucidated by GPC and ESR techniques.     

Cyclic acetal-photosensitized polymerization. II. Photopolymerization of styrene in the presence of various monocyclic acetals

The polymerization of styrene (St) in benzene solution in the presence of 1,3-dioxane (DON), 1,3-dioxepane (DOP), trioxane (TRON), or tetraoxane (TEON) by means of photoirradiation of the system at 40°C has been studied kinetically from the standpoint of photosensitized polymerization. The rate of photosensitized polymerization R_p increased in the order: DOP < DON < TRON < TEON, as shown by the rate constant of decomposition of cyclic acetals, and then could be expressed by R_p = k[monocyclic acetal]^0.5[St]^1.0. The polymerization was confirmed to proceed via a radical mechanism.     

Micelle formation of polystyrene-<Emphasis Type="Italic">block</Emphasis>-poly(4-<Emphasis Type="Italic">tert</Emphasis>-butoxystyrene) in hexane

A new type of hexane-soluble polymeric surfactant based on poly(4-tert-butoxystyrene) (P ^t BSt) was prepared by the nitroxide-mediated living radical polymerization, and their self-assemblies in hexane were explored. Polystyrene-block-P ^t BSt diblock copolymers with six different P ^t BSt block lengths were obtained by the sequential living radical polymerization of styrene followed by 4-tert-butoxystyrene using 4-methoxy-2,2,6,6-tetramethylpiperidine-1-oxyl as the mediator; Mn(P ^t BSt block) = 13,500, 21,700, 26,600, 47,500, 91,300, and 108,000 at the constant length of the PSt block (Mn = 12,900). Dynamic light-scattering studies demonstrated that the copolymers self-assembled into monodispersed spherical micelles in hexane. The hydrodynamic diameter of the micelles increased with an increase in the P ^t BSt block length. The micellar size also increased as the copolymer concentration increased. However, the size decreased as a result of the increasing temperature due to a decrease in the aggregation number. The ¹H NMR analysis confirmed that the copolymers formed micelles with PSt cores.     

Polymerization of Styrene Initiated by 1,4-Dimethyl-1,4-bis(p-anisyl)-2-tetrazene

Abstract

The polymerization of styrene (St) initiated by 1,4-dimethyl-1,4-bis(p-anisyl)-2-tetrazene (1a) was studied kinetically in benzene. The polymerization proceeds through a radical mechanism. The rate of polymerization is proportional to [1a]^0.5 and [St]^1.0. The overall activation energy for the polymerization is found to be 81.2 kJ/mol within the temperature range of 65 to 80°C. The activation parameters for the decomposition of 1a at 70°C are k_d = 1.88 × 10^?5s^?1, δH? = 133.1 kJ/mol, and δS? = 29.9 J/mol·deg.     

Kinetics of polymerization of styrene-in-water microemulsions

The kinetics of polymerization of styrene-in-water microemulsions was investigated using dilatometry. From plots of percentage conversion versus time, the rate of polymerization, R _p, was determined. From log-log plots of R _p versus styrene and initiator [2,2′-azobis(isobutyronitrile), AIBN] concentrations the following relationship was established: R _p∝ [styrene]^1.2 [AIBN]^0.46. These exponents are similar to those predicted by the theory of emulsion polymerization. The results also showed a rapid conversion in the initial period (interval 1) followed by a slower rate at longer times (interval 2). It was suggested that in interval 1, the main process in nucleation of the microemulsion droplets, whereas in interval 2 propagation is the more dominant factor. The rapid polymerization of microemulsions is consistent with their structure, whereby very small droplets with flexible interfaces are produced. Received: 2 March 1999 Accepted in revised form: 10 May 1999     

Kinetic study of the radical polymerization behavior of N‐(1‐phenylethylaminocarbonyl)methacrylamide

Polymerization of N‐(1‐phenylethylaminocarbonyl)methacrylamide (PEACMA) with dimethyl 2,2′‐azobisisobutyrate (MAIB) was kinetically studied in dimethyl sulfoxide (DMSO). The overall activation energy of the polymerization was estimated to be 84 kJ/mol. The initial polymerization rate (R_p) is given by R_p = k[MAIB]^0.6[PEACMA]^0.9 at 60 °C, being similar to that of the conventional radical polymerization. The polymerization system involved electron spin resonance (ESR) spectroscopically observable propagating poly(PEACMA) radical under the actual polymerization conditions. ESR‐determined rate constants of propagation and termination were 140 L/mol s and 3.4 × 10⁴ L/mol s at 60 °C, respectively. The addition of LiCl accelerated the polymerization in N,N‐dimethylformamide but did not in DMSO. The copolymerization of PEACMA(M₁) and styrene(M₂) with MAIB in DMSO at 60 °C gave the following copolymerization parameters; r₁ = 0.20, r₂ = 0.51, Q₁ = 0.59, and e₁ = +0.70. © 2005 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 43: 2013–2020, 2005     

Multibubble sonolysis and sonoluminescence in molten elementary sulfur and sulfur—styrene mixture

The effect of saturation with argon, as well as styrene and iodine additives on the temperature dependence of multibubble sonoluminescence intensity in molten sulfur at 120–230 °C was studied. The shape of the temperature dependence with a maximum at 170–200 °C is determined by the viscosity variations related to the changes in the molecular structure of molten elemental sulfur. At high temperatures, cyclooctasulfane (S₈) molecules break to radical products, which then undergo polymerization that can be slowed down by the additives. Sulfurization of styrene during sonolysis of a sulfur—styrene mixture resulting in products of the thiophene series was detected. Unlike thermal sulfurization that affords 2,5-diphenylthiophene as a major product, sonochemical sulfurization results mainly in 2,4-diphenylthiophene. The mechanism of 2,4-diphenylthiophene formation initiated by the reaction of styrene molecules with S⁺ ions produced upon fragmentation of S₈ within cavitation bubbles is proposed. The glow of electronically excited S⁺* ions is responsible for the band with a maximum at 560 nm in the sonoluminescence spectrum of molten sulfur, which is suppressed by the styrene additive.