THE AROMATIC AND HETEROCYCLIC DINITRILES AND THEIR POLYMERS. Ⅸ. THE POLYMERIZATION KINETICS OF 4, 4''-BIPHENYLDICARBONITRILE*

The polymerization kinetics of 4,4'-biphenyldicarbonitrile catalyzed by complex of 4,4'-biphenyl-dicarbonitrile with ZnCl_2 was studied. The cyano group concentration was measured by infrared spectroscopic analysis using potassium ferricyanide as the internal reference. The results proved that the polymerization is a second order reaction, and the activation energy of polymerization is 12.4 kcal/mol. The polymerization rates of 4,4'-biphenyldicarbonitrile catalyzed by other seven complexes were also measured. The polymerization mechanism was discussed.     

THE EFFECTS OF N-2-HYDROXYETHYL-N-METHYL-p-TOLUIDINE ON METHYL METHACRYLATE RADICAL POLYMERI-ZATION AND ACRYLONITRILE PHOTOINDUCED POLYMERIZATION

The effects of N-2-hydroxyethyl-N-methyl-p-toluidine (HMT) on MMA polymerization using organic peroxide as an initiator and on AN photoinduced polymerization have been investigated respectively. The kinetics of polymerization and the overall activation energy of polymerization were determined. Based on kinetics study and the end group analysis of the polymer obtained by UV spectrum method, the initiation mechanism is proposed.     

AROMATIC AND HETEROCYCLIC NITRILES AND THEIR POLYMERS ⅩⅦ. THE POLYMERIZATION KINETICS OF CYANOPYRIDINES AND CHARACTERIZATION OF THE FORMED POLYMER*

The polymerization rates of three cyanopyridines catalyzed by cuprous chloride-zinc system are measured, and the structure of the formed polymer is also determined. Compared with aromatic nitrile, cyanopyridines polymerize faster and form polyconjugated polymer with skeleton—(C=N)—_n instead of triazine structure. This chain-polymer possesses semiconductive property, and can be converted into conductive material by thermal treatment. In addition, the polymerization kinetics of 3-cyanopyridine catalyzed by 3-cyanopyridinium perchlorate is investigated. It is found that the polymerization rate is directly proportional to the concentrations of monomer and catalyst, and the activation energy of the polymerization is 103.1 KJ/mol.     

AROMATIC AND HETEROCYCLIC NITRILES AND THEIR POLYMERS XIX:THE POLYMERIZATION OF SUBSTITUTED BENZONITRILES CATALYZED BY COBALTIC ACETYLACETONATE

The polymerization kinetics of 4, 4'-biphenyldicarbonitrile and other substituted ben-zonitriles catalyzed by cobaltic acetylacetonate was studied. The structure of polymer ofdifferent substituted benzonitrile was also determined. It is found that the rate of polymeri-zation and the structure of polymer is greatly affected by the substituent of benzonitriles.     

GROUP TRANSFER POLYMERIZATION OF ETHYL ACRYLATE WITH LEWIS ACID CATALYST

This paper reports the kinetics of group transfer polymerization (GTP)of ethyl acrylate (EA)with zinc iodide catalyst in 1,2-dichloroethane using dimethyl ketene methyl trimethylsilyl acetal (MTS) as initiator at 0℃and above 0℃. The amount of catalyst used was studied. When zinc iodide catalyst used is more than 10mol% relative to monomer, the rate of polymerization is proportional to the concentration of monomer, whereas zinc iodide catalyst used is less than 10 mol% of the monomer, the rate of polymerization is independent of the monomer concentration.In the GTP of EA an induction period was observed when the zinc iodide contents are less than l0mol%. If the reaction temperature is over 0℃, living species become unstable and diminish, leading to incomplete monomer conversion. The reaction curves equations are obtained. The polymers have narrow molecular weight distributions which are not changed as decreasing zinc iodide contents. The polydispersity is about 1.2.     

VINYL RADICAL POLYMERIZATION INITIATED WITH CERIC ION AND ETHYL N, N-DIETHYLDITHIOCARBAMYL ACETATE SYSTEM

Acrylamide polymerization initiated with a redox initiation system consisting of cericion and ethyl N, N-diethyldithiocarbamyl acetate (EDCA) has been studied. It was foundthat the polymerization rate equation is in good agrement with that of a redox initiatedpolymerization, and the overall activation energy of the polymerization was determinedto be 25.2kJ·mol~(-1). Accordingly, the system belongs to a redox initiator. The initiationmechanism was proposed based on the end group analysis using FT-IR, UV spectroscopies.Analysis results revealed that the N, N-diethyldithiocarbamyl radical produced from theredox reaction of EDCA with ceric ion can initiate acrylonitrile (AN) polymerization andform the end group on PAN. The resulting PAN was photopolymerized with butyl acrylate(BA) to form PAN-b-PBA block copolymer.     

SYNTHESIS AND CHARACTERIZATION OF COPOLYMER OF 2,5-BIS[（4-METHOXYPHENYL）OXYCARBONYL]STYRENE AND STYRENE WITH HIGH MOLECULAR WEIGHT

The random copolymers of styrene and 2,5-bis[(4-methoxyphenyloxycarbonyl)styrene] (MPCS) with different copolymerization ratio were synthesized by conventional free radical polymerization. The copolymer having high molecular weight was experimentally elucidated using a combination of proton nuclear magnetic resonance spectroscopy and gel permeation chromatography. The liquid crystalline behavior of the copolymer was studied using differential scanning calorimetry, X-ray diffractometry and polarized optical microscopy. It was found that the liquid crystalline behavior was dependent on the content of styrene. Experimental results show that the copolymer could turn into a liquid crystalline phase at about 180℃ when the content of styrene was less than 20%. The mechanical properties of the copolymer were also studied. Preliminary results indicate that the tensile strength decreases while the tensile modulus increases as the content of MPCS is increased.     

Ring-opening polymerization of L-lactide with rare earth aryloxides substituted by various alkyl groups

<正>Rare earth aryloxides substituted by various alkyl groups[Ln(OAr)_3]such as methyl,isopropyl and tertbutyl,were used as single component catalysts to affect ring-opening polymerization of L-lactide(LLA).The catalytic activity, polymerization characteristics,polymerization kinetics and the mechanism were studied.It was found that the catalytic activity of rare earth aryloxides is influenced by both the structure and the number of alkyl groups on the phenyl ring.The stronger the electron-donation ability of the alkyl group,the higher the catalytic activity will be.An increase in the number of the substitute group will result in a higher catalytic activity.Lanthanum tris(2,4,6-tri-tert-butylphenolate)[La(OTTBP)_3] exhibits the highest activity among all lanthanum aryloxides.According to the ~1H-NMR data,it was proposed that the LLA polymerization proceeded via a coordination-insertion mechanism involving cleavage of acyl-oxygen bond of the lactide.     

Kinetics of ring-opening polymerization of octamethylcyclotetrasiloxane in microemulsion

Polysiloxane latexes were prepared by microemulsion polymerization of octamethylcyclotetrasiloxane(D4) in the absence of co-emulsifier with octadecyl trimethyl ammonium chloride as a cationic emulsiner and potassium hydrate as an initiator.The particle size was determined by the dynamic light scattering(DLS) technique and the reaction rates of the polymerization were discussed.Furthermore,the kinetics was studied by an initial-rate method,and the effects of the monomer,emulsiner and initiator concentrations and the temperature on polymerization conversions were investigated.From the kinetic results,the rate of polymerization,R_p at 80 ℃ can be expressed as R_p = k[D4]~(0.79)[OTAC]~(0.64)[KOH]~(0.38) and the apparent activation energy(E_a),which was determined by half-period method,is 95.32 kJ mol~(-1).     

SYNTHESIS AND PROPERTIES OF ACRYLIC-BASED SUPERABSORBENTS WITH ENHANCED CROSSLINKING ON PARTICLE SURFACE

A series of acrylic-based superabsorbent resins were synthesized by inverse suspension polymerization, using potassium persulfate as the initiator, N, N＇-methylene bisacrylamide （BIS） and divinylbenzene （DVB） as the multiple crosslinking agents. The morphology of the resulting superabsorbent resins revealed by SEM demonstrated that a hard shell layer was indeed formed due to surface crosslinking. The swelling and deswelling properties, and the mechanical strength of superabsorbents were investigated. The results indicated that the adding time of DVB and the amount of DVB participated in the crosslinking show a significant influence on the properties of superabsorbents. When DVB was added in polymerization later, the amount of DVB participated in reaction decreases and the surface crosslinked shell becomes thinner. It is suitable for DVB to be introduced in the later stage of the polymerization process, because the absorption rate of resin is efficiently improved in conjunction with higher water absorption. Furthermore, it was found that the mechanical strength of swollen superabsorbent with surface crosslinking was indeed enhanced in comparison with that of the conventional one.     

STUDIES ON THE INITIATION MECHANISM OF CERIC ION AND ACETYLACETONE REDOX SYSTEM IN VINYL POLYMERIZATION

The initiation mechanism of acrylamide (AAM)polymerization using ceric ion/acetylacetone system as an initiator has been studied. The redox polymerization was revealed by the low value of overall activation energy of AAm polymerization. The structure of free radicals formed from above-mentioned initiation sytem were detected by radical trapping and ESR spectra techniques and the end groups of polymers obtained were determined by FT-IR spectra analysis method. Based on these results the initiation mechanism is proposed.     

AROMATIC AND HETEROCYCLIC DINITRILES AND THEIR POLYMERS. Ⅺ. STUDY ON THE POLYMERIZATION OF AROMATIC AND HETEROCYCLIC DINITRILES BY INFRARED SPECTROSCOPY*

The polymerization rates of fourteen aromatic and heterocyclic dinitriles were measured by infraredspectroscopy and compared with that of 4, 4′-biphenyldicarbonitrile. The rate is greatly enhancedwhen an electron withdrawing group is substituted at the para position of cyano group in aromaticdinitriles. The polymerization rates of heterocyclic dinitriles wer discussed in terms of π-lectrondensity of the heterocyclic rings.     

AROMATIC AND HETEROCYCLIC DINITRILES AND THEIR POLYMERS ⅩⅢ. POLYMERIZATION KINETICS OF BENZONITRILE AND THE STRUCTURE OF PRODUCTS

The polymerization kinetics of benzonitrile were studied, and the formation rate constants of s-triazine structure and linear polymer were determined. The influence of polymerization temperature and the amount of zinc chloride as catalyst on the ratio of linear to cyclic structure were also investigated, and the obtained results were discussed.     

THE POLYMERIZATION OF AROMATIC AND HETEROCYCLIC DINITRILES

This review is a concise survey about the works in our laboratory on the polymerization of aromatic and heterocyclic dinitriles, including the polymerization kinetics and mechanism, synthesis of heterocyclic dinitriles, the structure of polymers, and the correlation between the structures of dinitriles and polymerization rates and thermal performances of Polymers.     

The Photopolymerization Kinetics of Acryl amide Sensitized with Toluidine Blue-Alcoholamine Induced by He-Ne Laser

Toluidine blue(TB) is a good sensitizer for the polymerization of acrylnmide(AM) induced by He-Ne laser. With TB as a sensitizer and various alcoholamine as donors, the photoredox of TB and the polymerization kinetics of AM induced by He-Ne laser were investigated. It was found that either for the photoredox of TB or for the polymerization of AM, the activity of alcoholamine increases in the order of EOA相似文献   

THE STUDYOF SYNTHESIS AND CHARACTERISTICS OF POLYPHENYLACETYLENE USING WOBr_4AS CATALYST

A new kind of catalyst WOBr_4,which can be used in the polymerization ofphenylacetylene(PhA),has been synthesized.The obtained polyphenyl(?)cetylene(PPhA)using WOBr_4 as catalyst is soluble、fusible、with brown-red colour and has 1831(Mn).The analysis of the stucture of PPhA shows that the polymer has cis-transoidalstructure,therefore,the reaction mechanism is via complex catalysis.     

STUDIES ON THE INITIATION MECHANISM OF ORGANIC PEROXIDE AND N-METHACRYLOYLOXYETHYL-N-METHYL ANILINE IN METHYL METHACRYLATE POLYMERIZATION

The initiation mechanism of methyl methacrylate (MMA) polymerization by organic peroxide and polymerizable aromatic tertiary amine such as N-methacryloyloxyethyl-N-methyl aniline (MEMA) binary system has been studied. The kinetics of polymerization of MMA and the ESR spectra of organic peroxide/MEMA system were determined. Based on the ESR study and the end-group analysis by UV spectra of the polymer formed, the initiation mechanism is proposed.     

SYNTHESIS AND POLYMERIZATION OF BISPHENYLENE ORTHOCARBONATE

Bisphenylene orthocarbonate (Ⅱ) was synthesized by the reaction of dicopper catecholate with carbon tetrachloride, and underwent cationic ring-opening polymerization with the introduction of phenyl group into the main chain. The obtained polymer with ester and ether group was verified by IR and ~1H NMR spectra. Based on the analysis of the polymer structures, the polymerization mechanism was proposed. Its T_m and T_(?) are 254℃and 160℃respectively. No decomposition of the polymer was observed below 320℃. The volume expansion property of the monomer during polymerization was studied by measuring the density difference between Ⅰand its polymer at various temperatures.     

AROMATIC AND HETEROCYCLIC NITRILES AND THEIR POLYMERS ⅩⅧ. THE POLYMERIZATION KINETICS OF BENZONITRILE CATALYZED BY METAL ACETYLACETONATE

The bulk polymerization of benzonitrile catalyzed by Co(Ⅱ), Co(Ⅲ) and Fe(Ⅲ) acetylacetonate was studied. The results of kinetics study show that the rate of polymerization was proportional to first power of the concentration of catalyst and second power of the concentration of monomer.     

EFFECTS OF GELATION RETARDATION ON THERMAL RESPONSE BEHAVIOR OF PNIAPM GELS： A METHOD TO IMPROVE THEIR DESWELLING KINETICS

P(N-isopropylacrylamide)(PNIPAM)prepared by reversible addition fragmentation chain transfer(RAFT) polymerization exhibited gelation retardation.The intermediate before gelation was characterized and indicated the presence of branched or hyperbranched chains.The swelling behavior was investigated,and the gel by RAFT polymerization(RAFT gel)showed accelerated shrinking kinetics and higher swelling ratio comparing with conventional gels(CG).The study was extended to gels prepared by using 2-hydroxy-1-ethanethiol as chain transfer agent and by using low concentration solutions. The two systems also exhibited retardation effects and improved deswelling kinetics.The different swelling behaviors of these gels and CG could be attributed to the presence of dangling chains caused by gelation retardation.