Synthesis and characterization of a novel mid‐chain macrophotoinitiator of polyacrylonitrile by Ce(IV)/HNO3 redox system

The polymerization of acrylonitrile initiated by cerium(IV) ammonium nitrate in combination with dihydroxy functional photoinitiator namely, 2‐hydroxy‐1‐[4‐(2‐hydroxyethoxy)phenyl]‐2‐methyl propan‐1‐one (HE‐HMPP), Irgacure 2959, has been investigated in aqueous nitric acid. A novel mid‐chain macrophotoinitiator of polyacrylonitrile (PAN) was obtained. The effects of acrylamide (AAm), HE‐HMPP, Ce(IV), and HNO₃ concentrations and temperature on the polymerization rate, monomer conversion, and intrinsic viscosities were investigated. The photodegradation and IR, H NMR, UV, and fluorescence spectroscopic studies revealed that PAN with desired photoinitiator functionality in the middle of the chain was obtained. The obtained PAN was used as prepolymer for photoinduced free radical polymerization of methyl methacrylate (MMA) and AAm to produce block copolymers. © 2008 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 46: 5404–5413, 2008     

Grafting of Acrylamide On 1, 1, 2, 2-Tetra-Chloroethane Preswelled Polyethylene Terephthalate) Films Using Azobisisobutyronitrile Initiator

Abstract

Graft polymerization of acrylamide (AAm) on 1, 1, 2, 2 tetrachloro-ethane (TCE) preswelled poly(ethylene terephthalate) (PET) films were performed with chemical initiation method using asobisiso-butyronitrile (AIBN) initiator. Temperature was found to have a greater effect on the swelling then the swelling time. Variation of the graft yield with polymerization temperature, time, AIBN concentration, AAm concentration, AIBN and AAm inclusion times were investigated. The optimum temperature for grafting was found to be 70°CC. The graft yield was observed to increase with polymerization time, AAm concentration, initiator and monomer diffusion time up to a saturation graft yield and then leveled off. An increase in AIBN concentration first enhanced the percent grafting then showed a decrease. The addition of some salts (Ni²⁺, Cr³⁺, Co²⁺, Cu²⁺) on the rate of grafting was also investigated. From the temperature dependence of the initial rate of grafting, the overall activation energy was found to be 4. 1 kcal/mol and relevant rate equation have been derived. The effect of grafting on film propities, such as water absorption capacity, intrinsic viscosity were determined. Grafted films were characterized by FTIR spectros-copy and scanning electron microscopy (SEM).     

含胺基功能性单体的聚合研究 XIV.含二甲氨基丙烯酰类衍生物与过硫酸钾引发体系引发的丙烯酰胺聚合

The polymerization of acrylamide (AAm) initiated by the combination of N-(N', N'-dimethylaminomethylene)methacrylamide (DMAMMA) or N, N,-dimethylaminoethyl methacry-late with potassium persulfate were studied kinetically. The rate equation for the AAm polymerization initiated by the above initiation systems were given asRp- Kp[AAm][K₂S₂O₈]^1/2[DMAMMA]^1/2 Rp=Kp[AAm][K₂S₂O₈]^1/2[DMAEMA]^1/2 respectively. The overall activation energies for the above polymerization were determined to be 8.7 Kcal/mol and 9.2 Kcal/mol respectively. The UV analysis for the PAAm initiated by the above initiation systema showed that the polymerizable amines,DMAMMA and DMAEMA notonly joined the redox initiation but also incorprated into the AAm polymer chains. The super high molecule weight,10⁷of PAAm were obtained by using these initiation systems.     

RADIATION INDUCED ACRYLAMIDE/CITRIC ACID HYDROGELS AND THEIR SWELLING BEHAVIORS

Citric acid (CAc) moieties containing acrylamide (AAm) hydrogels were prepared by gamma irradiation of their aqueous solutions. A possible polymerization and crosslinking mechanism for acrylamide/citric acid (AAm/CAc) hydrogels is proposed. The effects of irradiation dose and citric acid content on swelling behavior were investigated. Swelling took place in water at 25°C and was followed gravimetrically. Incorporation of a relatively low amount of citric acid to acrylamide hydrogel increased its swelling up to 950% from 700%. The diffusion of water into AAm/CAc hydrogels was found to be a non-Fickian type. Diffusion coefficients of AAm/CAc hydrogels found as 5 × 10^?7? 10 × 10^?7 cm² sec^?1. It has also been found that the number average molar mass between crosslinks is increased with the CAc content and decreased with irradiation dose.     

Preparation of Fluorine-Containing Polyacrylate Emulsion by a UV-initiated Polymerization

A fluorine-containing polyacrylate emulsion was synthesized by a UV-initiated emulsion polymerization from methyl methacrylate (MMA) and hexafluorobutly methacrylate (HFMA) in the presence of 2-hydroxy-4-(2-hydroxyethoxy)-2-methyl-propiophenone (Irgacure 2959) as a hydrophilic photoinitiator at room temperature. The latex and films were characterized by Fourier transformed infrared (FT-IR) spectrometry, nuclear magnetic resonance (¹H-NMR, ¹⁹F-NMR) spectrometry, transmission electron microscopy (TEM), recycling gel permeation chromatography (GPC), dynamic light scattering (DLS), and contact angle (CA) analysis, respectively. The effects of photoinitiator and emulsifier concentration on the polymerization were discussed. Compared to the corresponding thermal polymerization, UV-initiated polymerization of the MMA/HFMA emulsion could be accomplished at a much higher speed. The polymerization conversion in UV-initiated polymerization reached 95% within 10 min at an emulsifier concentration of 0.6 wt%, photoinitiator concentration of 0.4 wt%, and monomer concentration of 10 wt%.     

4-N,N-Dimethylamino-4'-Isopropylbenzophenone as polymerization photoinitiator. Effect of solvent and photoinitiator concentration on its photoreactivity and on the polymerization process

Several kinetics aspects of the methyl methacrylate (MMA) polymerization using 4-dimethylamino-4'-isopropylbenzophenone (PI) as photoinitiator have been studied. The order of the polymerization reaction with respect to monomer and initiator concentrations have been investigated, as well as the polymerization behavior under well-stirred and unstirred conditions; values of initiation quantum yield (?_i) and k_p/k_t^1/2 have also been determined. It has been found that the nature of the polymerization-initiating radicals depends on the type of solvent and the photoinitiator concentration ([PI]). In cyclohexane solution and at low [PI] (< 5 x 10^-5M), the cyclohexyl radical is practically the only polymerization initiating radical, while at higher [PI] both radicals, cyclohexyl and the aminoalkyl derived from PI, participate in the initiation step, increasing the participation of the later as the [PI] increases. When benzene is used as solvent both phenyl and aminoalkyl radicals participate in the initiation step at any [PI] employed. Efficiencies of the radicals derived from solvent and photoinitiator have been determined.     

KINETICS AND MECHANISM OF PHOTOINDUCED POLYMERIZATION BY α,α-DIMETHOXY-α-PHENYL ACETOPHENONE

α,α-dimethoxy-α-Phenyl acetophenone (DMPA) is an efficient and thermally stable photoinitiator. Here its spectral characteristics in the transient state were shown. The transient species were identified as a benzoyl radical and a dimethoxyi benzyl radical that played a primary initiation role in polymerization. The kinetics and mechanism of the bulk polymerization of MMA were investigated. The exponent of DMPA concentration and k_p/k_1~(1/2) value were found to be 0.5 and 0.066 mol(-1/2)l~(1/2)s~(-1/2), respectively. The existence of oxygen led to obtain the polymer with higher molecular weight, which can be attributed to the occurrence of the subsequent polymerization induced by active polymer end group. In the photocrosslinking reaction, the dependence of DMPA content on initial rate has been found. A principal reason is that the sample contained higher percentage of DMPA has higher light-absorbed efficiency. In solid film, higher concentration of DMPA is permitted to be used because there is little excited state self-quenching effect in the rigid medium.     

Inverse microemulsion polymerization of oil-soluble monomers in the presence of hydrophilic polyacrylamide nanoparticles

A new method for preparation of modified polymer particles in two steps was proposed. Free radical polymerization of an oil soluble vinyl monomer like butyl acrylate in inverse microemulsion containing polyacrylamide particles led to the formation of modified, partly hydrophobized, polyacrylamide particles. For the first step of the process (preparation of polyacrylamide particles in inverse microemulsion) is typical a very high polymerization rate while for the second step (polymerization of an oil soluble monomer (methyl acrylate, ethyl acrylate, butyl acrylate 2-ethylhexyl acrylate, methyl methacrylate, styrene) in the presence of polyacrylamide particles in inverse microemulsion, the reverse is true. The polymerization of an oil soluble monomer in some instances leads to the formation of 2-phase or even 3-phase disperse systems. The polymeric products obtained after precipitation of the polymer particles from the inverse microemulsions by ethanol were extracted by water and/or toluene and analyzed for acrylamide content. The separated polymer product contained high content of acrylamide, AAm/oil soluble monomer (butyl acrylate BA, or styrene, S) copolymer (85% of AAm/BA, ≈ 99% of AAm/S) besides relatively small amounts of homopolymers of oil soluble monomers (15% of BA, ≈ 1% of S homopolymers).     

Vinyl polymerization of acrylonitrile by the cerium(IV)-propane-1,2-diol system

The polymerization of acrylonitrile (M) initiated by the Ce(IV)-propane-1,2-diol (R) redox system has been studied in aqueous sulphuric acid under nitrogen in the temperature range 30 to 40°. The rate of polymerization is proportional to [M]², [R] and [Ce(IV)]^?1 and the rate of ceric ion disappearance is proportional to [R], [Ce(IV)]. The effects of certain salts, acid, solvent and temperature on both rates have been investigated. A kinetic scheme has been proposed, and various rate and energy parameters evaluated.     

N－甲基丙烯酰－N＇－嘧啶哌嗪与过硫酸钾引发体系引发的丙烯酰胺聚合

queous solution polymerization of acrylamide (AAm) was demonstrated by using initiation system consisting of N-methacryloyl-N '-pyrimidinopiperazine (MPMP ) and persulfate (KPS). The polymerization rate equation was obtained to beR_p = K_p[MPMP]^1/2 [KPS]^1/2 [AAm]^1.0The overall activation energy for the polymerization was calculated by Arrhenius quation to be Ea= 5.6 KJ/mol. The redox nature for the polymerization was clarified. A super high molecular weight up to 10⁷ of PAAm was obtained by using this initiation system. From the fluorescent analysis, it was confirmed that MPMP not only acted as a component of the redox system, but also entered into the acrylamide polymer chains.     

Surface Grafting onto Barium Sulfate: Polymerization of Acrylamide Initiated by the System Consisting of Alcoholic Hydroxyl Groups on the Surface and Ceric Ion

Abstract

To modify the surface of barium sulfate, the grafting of polymers onto the surface by the polymerization of acrylamide (AAm) initiated by the system consisting of eerie ion and alcoholic hydroxyl groups on the surface was investigated. Barium sulfate modified by 12-hydroxystearate (BaSO₄-HS) was prepared by the reaction of barium chloride with sodium sulfate containing a small amount of sodium 12-hydroxystearate. The presence of 12-hydroxystearate groups on the BaSO₄ surface was confirmed by XPS analysis and infrared spectra. It was found that the graft polymerization of AAm is initiated by the system consisting of eerie ion and BaSO₄-HS to give poly (AAm)-grafted BaSO₄. This indicated that the grafted polymer chains are propagated from surface radicals formed by the redox reaction of eerie ion with 12-hydroxystearate groups on the surface. The polymerization rate (R _p) of AAm initiated by the redox system was given by R _p = k[AAm][Ce(IV)][BaSO₄-HS] where k is constant, [AAm] is AAm concentration, [Ce(IV)] is cerie ion concentration, and [BaSO₄-HS] is BaSO₄-HS concentration. The result suggested that in such an initiating system, the unimolecular termination of growing polymer radicals from the surface of BaSO₄ proceeds preferentially. Furthermore, by grafting of poly(AAm) onto the BaSO₄-HS surface, the wettability of the surface was found to turn from hydrophobic to hydrophilic.     

Kinetics of the decay of nitroxyl radicals during polymerization of a complex of acrylamide with bismuth nitrate

Kinetics of the decay of nitroxyl radicals during spontaneous polymerization of complexes of acrylamide (AAm) with Bi^III nitrate has been studied by ESR. From a comparison of the experimental and calculated kinetic curves, the initiation rate constant of polymerization has been determined. The approach proposed is suitable for determining the main kinetic characteristics of other polymerizable nonparamagnetic AAm complexes with metal nitrates.Translated fromIzvestiya Akademii Nauk. Seriya Khimicheskaya, No. 9, pp. 1572–1575, September, 1994.This work was carried out with the financial support of the Russian Foundation for Basic Research (Project No93-03-4162).     

Graphene oxide embedded P(AAm)/PANI cryogel polymer composites for sensor application against pesticide,nitro compound,and organic dyes

Abstract

Graphene oxide (GO) embedded superporous poly(acrylamide) (P(AAm)) cryogel composites (P(AAm)-GO) were prepared and used as conductive sensor materials. For this goal, the GOs flakes within superporous P(AAm) cryogels were reduced in-situ employing hydriodic acid (HI), hydrazine (N₂H₄), and sodium borohydride (NaBH₄) as reducing agents. Amongst all reduced agents\the highest conductivity was observed for HI reduced P(AAm)-GO (P(AAm)-rGO) with 1.7?×?10^?6±9.7?×?10^?8 S.cm^?1. Then again, this P(AAm)-rGO was used for in-situ synthesis of conductive polymers, poly(aniline) (PANI), and poly(pyrrole) (PPy) by using oxidative polymerization technique. The SEM, FT-IR, TGA and conductivity measurements were done for the characterization of prepared cryogel composites. It was found that the conductivity of P(AAm)-rGO increased 70- and 1400-fold with the presence of PANI and PPy, respectively. Furthermore, potential sensor application of P(AAm)-rGO/conductive polymers were tested against herbicides such as paraquat, glyphosphate (G), and a phenolic compound, 4-nitrophenol (4-NP), and some dyes such as methylene blue (MB), methyl orange (MO). Conductivity of P(AAm)-rGO/PANI decreased 5.3 -fold upon reacting with 10?mL 50?ppm G solution. The sensitivity and effect of G amounts were also tested for P(AAm)-rGO/PANI cryogel composite.     

Spectrophotometric determination of titanium(IV) as a mixed thiocyanate—monooctyl-α-anilinobenzylphosphonate complex

Extraction of titanium(IV) thiocyanate complexes by monooctyl-α-anilinobenzylphosphonate (MOABP) dissolved in chloroform has been investigated as a function of hydrochloric and sulfuric acid concentration. Chloroform solutions follow Beer's law and are stable for at least 24 h. A sensitive and reproducible spectrophotometric determination of titanium is possible. Two complexes were identified; the first formed at acid concentrations less than 1 M, has the ratio Ti:SCN:MOABP 1:1:2 and the second, formed at higher acidity, has the ratio Ti:SCN:MOABP 1:2:2. The method is based on the extraction of titanium thiocyanate with MOABP from either 0.5 M H2SO4, and measurement of the absorbance at 336 nm (? = 11 000 l mol^-1 cm^-1 ), or from 6.5 M HCl, and measurement of the absorbance at 420 nm (? = 22 000 l mol^-1 cm^-1). The polymerization of thiocyanate has been studied; isoperthiocyanic acid has been identified as the polymerization product. Although both procedures give reproducible results, extraction from 6.5 M HCl is more sensitive, fewer elements interfere, and the precipitation of isoperthiocyanic acid is avoided.     

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     

H NMR study of temperature-induced phase separation in solutions of poly(N-isopropylmethacrylamide-co-acrylamide) copolymers

¹H NMR spectroscopy was applied to investigate temperature-induced phase separation in solutions of poly(N-isopropylmethacrylamide-co-acrylamide) [P(IPMAm/AAm)] random copolymers in D₂O, D₂O/ethanol and D₂O/acetone. The NMR relaxation behaviour of water (HDO) was also examined. The effects of P(IPMAm/AAm) composition and the ethanol or acetone content in the mixed solvents on the temperature, width and extent of the phase transition as well as on the mobility of polymer segments and water molecules were characterized. For D₂O solutions of the copolymers prepared with the AAm fraction in the polymerization mixture not exceeding 25 mol% ¹H NMR spectra show dynamic heterogeneity of copolymer chains in mesoglobules where AAm sequences and surrounding short IPMAm sequences are hydrated and mobile, while sufficiently long IPMAm sequences are dehydrated and their mobility is strongly reduced. The obtained results are consistent with the idea that P(IPMAm/AAm) copolymer mesoglobules are rather porous and disordered.     

Polymerizabilities of Several Polar Vinyl Monomers by Imidazole

Polymerizabilities of several polar vinyl monomers in the presence of imidazole (Im) have been studied in CDC1₃ and CD₃OD by NMR spectra. Acrylic acid formed a bimolecular adduct with Im as the initial adduct, while methacrylic acid was not obtained, On the other hand, methyl acrylate, methyl methacrylate (MMA), acrylamide (AAm), and acrylonitrile formed the initial adduct between Im and monomer, respectively. In these monomers, AAm and MMA gave each polymer in tetrahydrofuranat room temperature. The number-average molecular weight ([Mbar]_n) of AAm polymers was determined to be in the range of 1000 to 1500, and the [Mbar]_n of MMA polymers was found to be in the range of 2500 to 4500, The rate of polymerization R_p was expressed by the equations R_p = k[Im][AAm] and R_p = k[Im] [MMA]², respectively. The activation energy E_R was obtained by Arrheniuss's plots as E_R(AAm) = 9.6 kcal/mol and E_R(MMA) = 3.8 kcal/mol. These polymerization mechanisms are discussed on the basis of these results.     

XPS analysis of the poly(ethylene terephthalate) film grafted with acrylamide

Graft polymerization of acrylamide (AAm) was performed onto the surface of a poly(ethylene terephthalate) (PET) film with the simultaneous UV irradiation method but using no photosensitizer and without degassing. To examine whether polyacrylamide (PAAm) was introduced into the bulk place of PET film by the surface graft polymerization, an x-ray photoelectron spectroscopic (XPS) study was performed on the PAAm-grafted PET films. The distribution of grafted PAAm chains on and in the PET films was estimated from the PAAm/PET ratio calculated from the XPS spectra of PET films with different amounts of grafted PAAm. The results clearly demonstrate that graft polymerization has actually occurred not merely on the outermost surface but also within the thin surface region of the PET film. In addition, the XPS analysis revealed that the PET component was always present in the grafted surface region by a mole fraction of 0.1 to 0.05 even when the amount of PAAm grafted was larger than 10 μg/cm².     

The influence of temperature and photoinitiator concentration on photoinitiated polymerization of diacrylate monomer

The behavior of p-methoxybenzoyldiphenylphosphine oxide, previously synthesized, as a photoinitiator for the polymerization of diacrylate monomer, in the presence of 3% (w/w) tertiary amine (triethyl amine) as synergist additive, was studied. The influence of temperature in the range 30–90°C at 3% (w/w) photoinitiator concentration and the influence of the photoinitiator concentration in the range 0.5–3.5% (w/w) at 30°C was investigated by differential scanning photocalorimetry (photo-DSC). In all experiments the photopolymerization was performed at constant light intensity (3 mW cm⁻²). The maximum conversion was obtained at temperature of 90°C at 3% (w/w) photoinitiator concentration and 3% (w/w) triethyl amine. The optimal concentration of photoinitiator to obtain maximum conversion was 3% (w/w), at 30°C. No thermal polymerization occurred at higher temperature.     

PHOTO-INDUCED GRAFT POLYMERIZATION OF ACRYLAMIDE ON POLYPROPYLENE MEMBRANE SURFACE IN THE PRESENCE OF DIBENZYL TRITHIOCARBONATE

Ultraviolet （UV）-induced graft polymerization of acrylamide （AAm） on polypropylene substrates was successfully conducted using dibenzyl trithiocarbonate （DBTTC） as photoinitiator. It was confirmed by chemical analysis and surface morphology observation with attenuated total reflectance Fourier transform infrared spectroscopy, X-ray photoelectron spectroscopy, and scanning electron microscopy. A possible mechanism for this graft process was presented, which suggested that, under UV irradiation, the C： S bond in DBTTC could split and abstract a hydrogen from the polypropylene surface and a surface free radical was then formed, and initiated the graft polymerization of AAm.