STUDIES ON RADICAL POLYMERIZATION OF METHYL METHACRYLATE INITIATED WITH ORGANIC PEROXIDE-AMINE SYSTEMS

Radical polymerization of methyl mcthacrylate (MMA) initiated with various diacyl peroxideamine systems was studied. Benzoyl peroxide (BPO) and lauroyl peroxide (LPO) were used as diacyl peroxide component, N,N-dimethyl aniline (DMA) and its para substituted derivatives, i.e., N,N-dimethyl-p-toluidine (DMT), p-hydroxymethyl-N,N-dimethyl aniline (HDMA), p-nitro-N,N-dimethyl aniline (NDMA) and p-dimethylamino benzaldehyde (DMAB) were used as amine components. It was found that the peroxide-DMT systems give higher rates of bulk polymerization R_p of MMA than the organic hydroperoxide-DMT systems with the following descending order BPO-DMT>LPO-DMT>CHP (cumene hydroperoxide)-DMT>TBH (tert-butyl hydroperoxide)-DMT. The aromatic tertiary amines possess obvious structural effect on the R_p values in the diacyl peroxideamine system. The overall activation energy of MMA polymerization was determined and thekinetics of polymerization of MMA initiated with BPO-DMT system was investigated.     

STUDIES ON THE ORGANIC PEROXIDE-DITERTIARY AMINE INITIATION SYSTEMS

Radical polperization of methyl methacrylate (MMA) initiated with organic peroxide-ditertiaryamine binary systems was studied. Benzoyl peroxide (BPO), lauroyl peroxide (LPO), t-butyl hydro-peroxide (TBH), and t-butyl peroxybenzoate (TBPB) were used as organic peroxide components,aromatic ditertiay amine 4, 4′-tetramethyldiaminodiphenylmethane (TMDAPM) an d aliphatic di-tertiary amine tetramethylethylenediamine (TMEDA) were used as amine components. The polymeri-zation rate R_P, the overall activation energy of polymerization E_a, the rate equation of MMA poly-merization, and the end group of polymer formed were determined.     

THE INWARD H+ PATHWAY IN BACTERIORHODOPSIN: THE ROLE OF M412 AND P(N)560 INTERMEDIATES*

Abstract— In purple bacteriorhodopsin sheets adsorbed onto the phospholipid-impregnated collodion film, electrogenic stages are identified correlating with decays of the M and N(P)-type intermediates. It is concluded that both M → N and N → bR transitions are electrogenic.
The M decay is shown to be of a complex kinetics. In purple sheets, the lower the light intensity, the higher the rate of "slow M" decay. Such a dependence, which is absent from monomeric bacteriorhodopsin in proteoliposomes and from Triton X-100-solubilized protein, may be explained by the inhibiting effect of a light-induced conformation change in a bacteriorhodopsin molecule upon the M decay in some other bacteriorhodopsin molecules within the same sheet.
The light intensity-independent "slow M" decay in solubilized bacteriorhodopsin is shown to correlate with the decay of the N intermediate and H⁺ uptake after the flash. In contrast to "fast M", "slow M" is pH dependent, closely resembling in this respect the N intermediate. It is suggested that there is a fast light-independent equilibration between M and N so that "slow M" represents the portion of the M pool that monitors the N concentration. The M → N equilibrium is assumed to be involved in the effect of the light-induced electric field on the M decay. No direct effect of light on the equilibrium was found.     

STUDIES ON THE KINETICS OF PROPYLENE POLYMERIZATION WITH THE COMPLEXTYPE TiCl_3 CATALYST

The active center concentration C_p, the rate constant k_p, and the activation energy of chain propagation E_p in the polymerization of propylene with complex-type TiCl_3-(C_2H_5)_2AlCl catalyst system were studied. The Mn was corrected by (?) value determined by GPC. The values thus obtained for C_p, k_p, and E_p at 50℃were 3.01 mol/mol Ti, 6.27 1/mol·sec, and 5.10 Kcal/mol respectively.The kinetic parameters were compared with those obtained from conventional TiCl_3·AlCl_2 catalyst, showing that the higher activity of the complex-type catalyst over the conventional catalyst is not only due to the higher C_p of the former, but to a greater extent due to the increase of the k_p value.     

THE ROLE OF O2- IN THE CHEMILUMINESCENCE OF LUMINOL*

Abstract— The chemiluminescence of luminol in buffered aqueous solutions is inhibited by superoxide dismutase. This occurs whether the luminescence is induced by ferricyanide, persulfate, hypochlorite, or by the action of xanthine oxidase on xanthine. Since superoxide dismutase inhibits reactions which involve O₂^-, we conclude that this radical is a constant factor in the chemiluminescence of luminol in aqueous solutions. The kinetics of light production are discussed in terms of hypothetical mechanisms that fit the available data. The strong luminescence of luminol in aprotic solvents or in aqueous systems containing relatively high concentrations of H₂O₂ could not be explored in this way, because superoxide dismutase is inactive under such conditions.     

STUDIES ON THE POLYMERIZATION OF 2,2,6,6-TETRAMETHYL PIPERIDINYL METHACRYLATE

The radical homo-and co-polymerization of 2,2,6,6-tetramethyl piperidinyl methacrylate (TM-PM) with various initiators have been studied. It was found that, with azo-type initiators, the poly-merization proceeded readily, while with acyl peroxide initiators, the polymerization was inhibitedeffectively because of the formation of the stable TMPM-oxyl radical, identified by ESR. Thisobservation was further confirmed by the absence of inhibition effect on the addition of 2,2,6,6-tetramethyl 4-piperidinol to the polymerization system, whereas remarkable inhibition was observed onthe addition of the stable 2,2,6,6-tetramethyl 4-piperidinol N-oxyl radical. The reaction mecha-nism was discussed. We also found that when TMPM reacted with BPO in petroleum ether, N-benzoyloxy 2,2,6,6-tetramethyl 4-piperidinyl methacrylate was formed, and this novel compound has been characterizedwith IR, ESR, NMR and Mass Spectroscopy.     

STUDIES ON THE OXIDATION AND GRAFT COPOLYMERIZATION OF POLYETHERS

Polyethers could form hydroperoxide under air-oxidation or photo-oxidation in the presence of H_2O_2. The scission of ether linkage induced by moderate oxidation was prevented by controlling the reaction time and hydroperoxide concentration. The oxidation rate was affected by the end groups of polyethers. The decreasing order of oxidation rate for various poly(tetramethylene ether) glycol derivatives having different end groups are as follows: poly(tetramethylene ether) glycol (PTMG)>poly(tetramethylene ether)acetate (PTMGAC) >poly(tetramethylene ether) phenyl carbamate (PTMGPC). The urethane end groups in PTMGPC increase the resistance toward oxidation. Polyether hydroperoxide reacts with ferrous ion or N,N-dimethyl toluidine (DMT) to form polymericoxy radical which then initiates the graft copolymerization of vinyl monomers at low temperature, and was devoid of homopolymerization. The copolymer after separation and purification was proved to be a graft one by IR analysis and elemental analysis.     

STUDIES ON THE POLYMERIZATION OF β-CYCLODEXTRIN WITH EPICHLOROHYDRIN*

Different proportions of β-cydodextrin and epichlorohydrin were used to prepare a group of β-cyclodextrin polymers. The relationship between the reaction extent and the molar ratios of reactants was discussed according to the results of ~1H-NMR, ~(13) C-NMR spectra and elemental analysis. Especially, high resolution ~1H-NMR spectra were usd for studying the reaction active sites and the extent of reaction. The solubility of oil soluble drugs in water was largely improved in the presence of water-soluble β-cyclodextrin polymer.     

DETERMINATION OF THE BINDING CONSTANT OF H14 CO−3 TO THE PHOTOSYSTEM II COMPLEX IN MAIZE CHLOROPLASTS: EFFECTS OF INHIBITORS AND LIGHT

The binding (dissociation) constant for HCO^?₃ to the photosystem II complex in maize chloroplasts is approximately 80 μM. One HCO^?₃ binds per 500–600 chlorophyll molecules. In the dark, formate is a competitive inhibitor of HCO^?₃ binding, while 3-(3′,4′-dichlorophenyl)-1, 1-dimethylurea (DCMU) inhibits HCO^?₃ binding non-competitively. Light decreases HCO^?₃ binding in the presence of formate. Light increases the binding of HCO^?₃ in the presence of DCMU. The high binding constant for HCO, discriminates strongly among the various hypotheses attempting to explain the “bicarbonate-effect” on photosystem II. The proposal by Stemler and Jursinic (Arch. Biochem. Biophys. 221, 227–237 1983), that HCO^?₃ is one of a class of monovalent anionic inhibitors of photosystem II, is favored. These anions compete for a specific binding site on the photosystem II complex.     

PROTOCHLOROPHYLL(IDE)630 PHOTOSENSITIZES ACTIVE Ca2+ ACCUMULATION IN MICROSOMAL AND MITOCHONDRIAL FRACTIONS ISOLATED FROM PLANTS

Abstract— White light irradiation of a microsomal fraction from etiolated plants affects their ATP-dependent Ca²⁺ accumulation by inhibiting active uptake and enhancing passive efflux. The succinate-dependent mitochondrial Ca²⁺ accumulation as well is decreased by light. The wavelength dependence of these light effects as well as their low quantum yield suggest non-phototransformable protochloro-phyll(ide) [PChl(ide)] to be the photoreceptor. PChlide has been isolated from corn leaves pretreated with 5-amino levulinic acid. Addition of Pchlide causes photosensitization of an otherwise light insensitive microsomal Ca²⁺ accumulation. The observed light effect may be due to contamination of the mitochondrial as well as the microsomal fractions with PChl(ide)‡ containing particles. Irradiation of the intact tissue leads to the almost complete disappearance of the light effect on the in vitro Ca²⁺ accumulation.     

AN 125I-LABELED N6-SUBSTITUTED AZIDO ANALOG OF NAD+ FOR THE PHOTOAFFINITY LABELING OF NAD+-LINKED ENZYMES

Abstract ¹²⁵I- N ⁶-(N-[6-N-{5-iodo-4-azidosalicyl}-aminohexyl]-aminocarbamoylmethyl)-nicotinamide adenine dinucleotide (¹²⁵I- N ⁶-I-ASA-AH-NAD⁺) was synthesized by coupling N ⁶ -([6-aminohexyl]-carbamoylmethyl)-NAD⁺ with 4-azidosalicylic acid N-hydroxysuccinimide ester followed by radioiodination. The utility of ¹²⁵I-N ⁶ -I-ASA-AH-NAD⁺ as an effective site-directed photoprobe was demonstrated by the photolabeling of both glutamate dehydro-genase and 15-hydroxyprostaglandin dehydrogenase. Both enzymes can be saturated with labeled probe with apparent dissociation constants comparable to those reported for NAD⁺. Photoincorporation of the probe into both enzymes was found to be protected specifically by NAD⁺. These results indicate that ¹²⁵I- N ⁶-I-ASA-AH-NAD⁺ can be a specific photoprobe for NAD⁺-linked enzymes.     

THE COORDINATION ADSORPTION OF AMINES ON CARBOXYL RESIN IN Cu~(2+) FORM FROM NON-AQUEOUS MEDIUM AND DESORPTION WITH ANHYDROUS ELUANT

The adsorption of aniline, N-methylaniline and N,N-dimethylaniline onto carboxyl resin in Cu~(2+) form from water,ethanol and n-hexane have been studied. The results show that the adsorption affinities from n-hexane are higher than thatfrom water, and nearly zero from ethanol. The separation factors for the adsorption of these three amines from mixed solutionwere also examined. The results of continuous column operations show that the breakthrough capacity of aniline from n-hexane reaches 90 mg/g dry resin in Cu~(2+) form, and the amines adsorbed can be stripped with anhydrous ethanol effectively.Adsorption onto carboxyl resin in Cu~(2+) form from non-aqueous medium and desorption with anhydrous eluant can overcomethe run-off of Cu~(2+) from the resin, and would show potential advantages in the separation of some water-insoluble naturalproducts.     

MORPHOLOGICAL STUDIES OF PET FILMS WITH DIFFERENT CRYSTALLIZATION RATE IN DRAWING PROCESSES

Morphological changes during stretching of two PET samples (S and T) with different crystallization rate have been studied by means of SALS, solvent etching and polarizing microscope techniques. Results show that under the same drawing conditions larger and more perfect rod-like and spherulitic superstructures were formed more easily in the sample with higher crystallization rate (sample S). The amount of less compact regions which may be easily attacked by the vapor of allyl amine decreases more rapidly in sample S than in sample T during stretching, and these regions are more randomly distributed in sample T especially at low elongations. The difference of the two samples in morphological changes is coincident with their difference in tensile behavior.     

THE INWARD H+ PATHWAY IN BACTERIORHODOPSIN: THE ROLE OF M412 AND P(N)560 INTERMEDIATES

Abstract
In purple bacteriorhodopsin sheets adsorbed onto the phospholipid-impregnated collodion film, electrogenic stages are identified correlating with decays of the M and N(P)-type intermediates. It is concluded that both M N and N bR transitions are electrogenic.
The M decay is shown to be of a complex kinetics. In purple sheets, the lower the light intensity, the higher the rate of "slow M" decay. Such a dependence, which is absent from monomeric bacteriorhodopsin in proteoliposomes and from Triton X-100-solubilized protein, may be explained by the inhibiting effect of a light-induced conformation change in a bacteriorhodopsin molecule upon the M decay in some other bacteriorhodopsin molecules within the same sheet.
The light intensity-independent "slow M" decay in solubilized bacteriorhodopsin is shown to correlate with the decay of the N intermediate and H⁺ uptake after the flash. In contrast to "fast M", "slow M" is pH dependent, closely resembling in this respect the N intermediate. It is suggested that there is a fast light-independent equilibration between M and N so that "slow M" represents the portion of the M pool that monitors the N concentration. The M N equilibrium is assumed to be involved in the effect of the light-induced electric field on the M decay. No direct effect of light on the equilibrium was found.     

STUDIES ON THE MECHANICAL PROPERTIES AND CRYSTALLIZATION BEHAVIOR OF POLYETHYLENE COMPOSITES

The effects of inter facial modifier on the mechanical, dynamic mechanical properties andcrystallization behavior of the polyethylene composites were investigated in the present paper.It was found that the interfacial modifer significantly improved the mechanical properties,influenced the dynamic mechanical spectra and slightly changed the crystallization behavior.The results showed that the interfacial modifier changed the dispersion state of dispersedphase of the composites, resulting in different phase structure, which was the major reasonIeading to different mechanical and crystallization properties.     

SIMULTANEOUS MEASUREMENT OF FREE RADICAL DECAY IN POLYMERIZATION OF MMA INITIATED BY AIBN USING ESR AND ITS KINETIC MODEL*

 The kinetics of free radical decay in the polymerization of MMA initiated by AIBN was studied by means of ESR spectroscopy. It was found that the curves of radical decay are strongly associated with the reaction temperature, the initiator concentration and the solvent. In the case of the radical polymerization carried out at high temperature or in solution, the radical concentration first reached a maximum, then declined monotonously with reaction time. It was also found that the greater the amount of initiator or the higher the temperature, the more rapidly the radicals decay. When the bulk polymerization was implemented at a relatively low temperature, the curves of radical decay became more complicated, i.e.,the radical concentration rapidly rose to a maximum, then dropped to a minimum, finally increased again with reaction time.Taking into account the diffusion effect, a semi-empirical equation is suggested to describe the kinetics of propagating radical decay.     

THE INFLUENCE OF SUBSTITUENTS IN METALLOCENE ON PROPYLENE POLYMERIZATION*

Two new unbridged zirconocenes, bis(2,4,7-trimethyl indenyl)zirconium dichloride (Met-Ⅰ) andbis(2-methyl-4,7-diethyl indenyl)zirconium dichloride (Met-Ⅱ) were prepared in order to investigate thesteric effects of substituents on the nature of the catalysts for the polymerization of propylene. A mixture ofmethyl aluminoxane (MAO) and triisobutylaluminum [Al(iBu)_3] was used as cocatalyst to activate thesecatalysts. The decrease in steric bulkiness of substituents at 4 and 7 positions of the indenyl ring resulted inan increase of both activity and molecular weight as well as the isotacticity.     

ON THE NATURE OF THE INTERMEDIATE ELECTRON ACCEPTOR (A1) IN THE PHOTOSYSTEM I REACTION CENTER

Abstract— A sodium dodecyl sulfate-Photosystem I (PSI) complex has been prepared and characterized with respect to its electron acceptors. Component X and iron-sulfur centers A and B are absent from this preparation but the intermediate electron acceptor (A₁) is present. Flash-induced absorbance changes at 25°C show charge separation, followed by a back-reaction with a half-time of 5 µs. The spectrum of the flash-induced change from 350 to 550 nm indicates a contribution from the intermediate electron acceptor, A₁, as well as from P700⁺. EPR studies show that A₁ is associated with a free-radical signal having a g-value of 2.0025 and a linewidth of 12 gauss. A, would appear to be associated with a monomeric form of either Chi α or pheophytin a.     

STUDIES ON THE INTERFACIAL ADHESION BETWEEN FUNCTIONALIZED POLYPROPYLENE AND POLYAMIDE 1010*

The interface behavior of polyamide 1010 (PA1010) and polypropylene (PP) was studied. In orderto improve their interfacial adhesion, functional PP was prepared by means of grafting glycidyl methacrylate(GMA) on PP main chains and used instead of plain PP. Several technological characterizations wereperformed here on their interfaces. ESCA was used to confirm that some kind of reaction occurred betweenend groups of PA1010 and epoxy species of PP-g-GMA. The peel test was adopted to measure interfacialadhesion. It was found that the fracture energy of interfaces between PA1010 and PP-g-GMA wasdramatically increased with the content of GMA. Their interfaces were observed as being blurred by usingSEM and TEM and a crack that could be seen in the case of the interfaces of the PA1010 and the plain PPdisappeared.     

STUDIES ON THE PERMEABILITY OF P VC/EBBA OVERLAPPED ULTRATHIN COMPOSITE MEMBRANES MODIFIED BY PLASMA-POLYMERIZATION WITH FLUOROCARBON MONOMERS

The PVC/EBBA ultrathin composite membranes with thickness of about 100 nm were prepared by spreading the solution on water surface. The overlapped composite membrane showed a characteristic aggregation structure in which the polymer matrix exists as a three-dimensional spongy network and the liquid crystal domains werc observed. Tne surface modification for the overlapped membranes was carried out by means of plasma-polymerization with the monomers of fluorocarbon compounds. Both Arrhenius plots of permeability coefficients for oxygen ((?)_O_2) in the membrane samples before and after modification showed significant increase in the vicinity of the T_(KN) of EBBA.