摘要:

AbstractAcrylamide was copolymerized withN,N′‐methylene‐bis‐acrylamide (NNMBA), tetraethyl‐eneglycol diacrylate (TEGDA), and divinyl benzene (DVB) in different proportions to afford crosslinked polyacrylamides with varying nature and extent of crosslinking. These insoluble polymers were functionalized with theN‐bromoamide function and the reactivity of the resulting polymericN‐bromoamide was investigated under different conditions. The capacities of the reagents varied from 6.7 mequiv / g for the linear polymeric reagent to 1.1 mequiv / g for the 15% DVB‐crosslinked reagent. Oxidation of benzoin to benzil was used as the model reaction. Investigation of the reaction under different conditions of solvent and varying molar excess revealed a significant influence of the nature and extent of crosslinking in deciding the extent of reaction. In the case of NNMBA‐crosslinked reagents, the reactivity increased up to 10% crosslinking and then decreased. The reactivity of the reagents increased up to 15% crosslinking in the case of TEGDA‐crosslinked ones and for DVB‐crosslinked reagents the reactivity decreased with crosslinking. The polarity of the crosslinking agent and its molar percentage on the polymeric reagent (crosslink density) are factors affecting the solvent compatibility, which in turn, is decisive in the facilita

ISSN:0887-624X    

DOI:10.1002/pola.1990.080281001

出版商:John Wiley&Sons, Inc.    

年代:1990

数据来源: WILEY

摘要:

AbstractN‐phenyl‐α‐methylene‐β‐lactam (PML), a cyclic analog ofN,N‐disubstituted methacrylamides which do not undergo radical homopolymerization, was synthesized and polymerized with α,α′‐azobis (isobutyronitrile) (AIBN) in solution. Poly (PML) (PPML) is readily soluble in tetrahydrofuran, chloroform, pyridine, and polar aprotic solvents but insoluble in toluene, ethyl acetate, and methanol. PPML obtained by radical initiation is highly syndiotactic (rr = 92%), exhibits a glass transition at 180°C, and loses no weight upto 330°C in nitrogen. The kinetics of PML homo‐polymerization with AIBN was investigated inN‐methyl‐2‐pyrrolidone. The rate of polymerization (Rp) can be expressed byRp=k[AIBN]0.55[PML]1.2and the overall activation energy has been calculated to be 87.3 kJ/mol. Monomer reactivity ratios in copolymerization of PML (M2) with styrene (M1) are r1= 0.67 and r2= 0.41, from whichQandevalues of PML are calculated a

ISSN:0887-624X    

DOI:10.1002/pola.1990.080281002

出版商:John Wiley&Sons, Inc.    

年代:1990

数据来源: WILEY

摘要:

AbstractSeveral CW–V catalysts were prepared by supporting VCl4on Mg Cl2with ethyl benzoate and CH–V catalysts prepared by reacting MgCl2.ROH, phthalic anhydride, and VCl4. These vanadium catalysts, activated with TEA (triethyl aluminum)/MPT (methyl‐p‐toluate) produce mainly (88–96%) refluxingn‐heptane insoluble isotactic PP. The active site has\documentclass{article}\pagestyle{empty}\begin{document}$ k_{p,i} = 1580 \left( M {\rm s} \right)^{ - 1}, k_{tr,i}^{\rm A} = 2 \times 10^{ - 3} {\rm s}^{ - 1} , k_{tr}^{\rm H} = 3.8 \times 10^{ - 2} \left( {\rm torr} \right)^{ - {1 \mathord{\left/ {\vphantom {1 2}} \right. \kern-\nulldelimiterspace} 2}} {\rm s}^{ - 1}$\end{document}for the isospecific ones and\documentclass{article}\pagestyle{empty}\begin{document}$ k_{p,a} = 58 \left( M {\rm s} \right)^{ - 1} ,k_{tr,a}^{\rm A} = 3 \times 10^{ - 3} {\rm s}^{ -1}$\end{document}for the nonspecific sites. Catalyst of VCl3supported on MgCl2has comparable productivity as the VCl4/MgCl2catalyst but catalyst of VCl2supported on MgCl2exhibit only one‐ninth of the productivity. Extensive comparison has been made between the CW–V and the CW–Ti systems which revealed striking similarities between their polymerization behaviors. MgCl2exerts profound influence on the stereochemical control of the vanadium ion on its activity for monomer coordinat

ISSN:0887-624X    

DOI:10.1002/pola.1990.080281003

出版商:John Wiley&Sons, Inc.    

年代:1990

数据来源: WILEY

摘要:

AbstractA novel substituted acetylene monomer, 4,4′‐(1,2‐ethynediyl) bis (phthalic anhydride) (EBPA) was made in six steps from 4‐nitro‐N‐methylphthalimide (4‐NPI) including two palladium‐catalyzed acetylene coupling steps. Several new polyimides were prepared from this monomer and six aromatic diamines. In addition, copolymers were made with EBPA and BPADA withmeta‐phenylene diamine. All of the polymers had high glass transition temperatures, high thermal stability and good solvent resistance. The copolymer containing twenty % EBPA had a glass transition temperature 33°C higher than Ultem® (a registered trademark of GE) and improved

ISSN:0887-624X    

DOI:10.1002/pola.1990.080281004

出版商:John Wiley&Sons, Inc.    

年代:1990

数据来源: WILEY

摘要:

Abstract9,10‐Diethynylanthracene was prepared by the alkaline hydrolysis of 9,10‐bis (trimethylsilylethynyl) anthracene. Another new monomer of 9, 10‐anthracenedithiol was prepared by the reduction of anthracene polydisulfide. A crystalline conjugated polymer of 9,10‐diethynylanthracene with 9,10‐anthracenedithiol was synthesized in a THF solution at 50°C by UV irradiation or by using radical initiators. The molecular weight (M̄n) of the insoluble polymer in THF is about 20000–30000 and the soluble is about 4000. From the sulfur content and IR spectrum of the insoluble polymer, it is realized that the obtained polymer has the alternating structure consisting of 9,10‐diethynylanthracene and 9,10‐anthracenedithiol units. X‐ray pattern indicated that the polymer has a layer structure. The conductivity of the undoped polymer was about 10−11S/cm, but enhanced up to 10−6S/cm by doping with iodine. The enhancement of the conductivity seems to be the existence of the CT complex among the polymer backbone and

ISSN:0887-624X    

DOI:10.1002/pola.1990.080281005

出版商:John Wiley&Sons, Inc.    

年代:1990

数据来源: WILEY

摘要:

AbstractA new method is described for the preparation of sterically stabilized nanoparticles of defined size and polydispersity which are stabilized in aqueous solution by the presence of covalently linked monomethoxy–poly (oxyethylene) (MeOPOE) chains. The nanoparticles (100–270 nm mean diameter) were prepared by a process of desolvation of a graft copolymer prepared from poly(2‐aminoethylmethacrylate) (PAEMA) and MeOPOE. Reproducible desolvation was achieved by the addition of sodium phosphate buffer to the copolymer in aqueous solution to give particles which were crosslinkedin situwith the addition of glutaraldehyde. The size (mean diameter) and polydispersity (Q) of the particles were determined by Photon Correlation Spectroscopy (PCS). The temperature at which the desolvation reaction was performed was found to influence the particle size; at low temperatures (5–12°C), small particles were produced (99–121 nm,Q= 0.090–0.121), whereas at much higher temperatures (40–55°C), particles as large as 224–275 nm (Q= 0.138–0.127) were generated. Other parameters such as the graft copolymer concentration, the amount of glutaraldehyde added, the pH of the sodium phosphate buffer added, and the reaction time were found to be of relative insignificance in influencing the particle size. In addition to those involved in drug delivery, our method of nanoparticle preparation may be of interest to those engaged in the preparation of particulate materials and colloidal dispersions for other specific applications (e.g. stabilized phot

ISSN:0887-624X    

DOI:10.1002/pola.1990.080281006

出版商:John Wiley&Sons, Inc.    

年代:1990

数据来源: WILEY

摘要:

AbstractHigh molecular weight block interrupt polysilane derivatives have been prepared by the condensation of a number of α,ω‐dichloropolysilanes with some aromatic bis silanols. In this manner, polymers containing polysilane blocks of 2, 4, or 6 catenated silicon atoms have been prepared. The materials are thermally stable and the UV spectroscopic properties mimic those of the corresponding monomers. Although these materials bleach upon irradiation in the deep UV, surprisingly, the block interrupt polysilanes behave as negative resists upon exposure to 254 nm radiation. This behavior contrasts with that of standard polysilane homopolymers which usually function in a positive lithographic m

ISSN:0887-624X    

DOI:10.1002/pola.1990.080281007

出版商:John Wiley&Sons, Inc.    

年代:1990

数据来源: WILEY

摘要:

AbstractA series of halogen‐containing poly (esterurethane)s was synthesized from the prepolymers, i.e., hydroxy‐terminated polyesters containing chlorine and fluorine and the diisocyanates such as toluene diisocyanate (TDI) and hexamethylene diisocyanate (HMDI). Polyesterification of halogenated phthalic anhydride with an excess of diols such as ethylene glycol, 1,2‐propanediol, and 1,4‐butanediol in the presence of trifluoroacetic anhydride (TFAA) was carried out to prepare prepolymers. The prepolymers and the poly (esterurethane)s were characterized by infrared (IR),1H nuclear magnetic resonance (NMR), viscosity, end‐group analysis, solubility and thermal analysis namely thermogravimetric analysis (TGA), and differential scanning calorimetry (DSC). Kinetics of thermal degradation was also studied. Resistance of the polymers to alkaline agents and combustion was al

ISSN:0887-624X    

DOI:10.1002/pola.1990.080281008

出版商:John Wiley&Sons, Inc.    

年代:1990

数据来源: WILEY

摘要:

AbstractSome mathematical models of the initial stage of the thermal degradation of the low molecular weight models for the normal units of PVC have been considered. The equations have been deduced. If the values of the average length of kinetic chain of dehydrochlorination of the polymer and the model compound are equal to each other, these equations may be used for the thermal degradation of idealized PVC.

ISSN:0887-624X    

DOI:10.1002/pola.1990.080281009

出版商:John Wiley&Sons, Inc.    

年代:1990

数据来源: WILEY

摘要:

Abstract4‐Vinylpyridinium trifluoromethanesulfonate monomers substituted at nitrogen with H, O, CH3, C2H5, C6H13, and C12H25were synthesized and characterized spectroscopically. Thermal analyses (DSC and TGA) were carried out on all the compounds. The solid monomers (NH, NCH3, NC6H13, and NC12H25) exhibited endothermic melting followed by exothermic polymerization and exothermic decomposition (>400°C). Liquid NC2H5monomer revealed only exothermic polymerization and decomposition. The NO polymer underwent thermal decomposition below 300°C. The N–C12H25homopolymer, prepared from monomer in the DSC or in bulk, displayed an unusual thermal transition at 250°C, which has been attributed to a polymer backbone reorientation leading to side‐chain ordering o

ISSN:0887-624X    

DOI:10.1002/pola.1990.080281010

出版商:John Wiley&Sons, Inc.    

年代:1990

数据来源: WILEY