Sorption properties of polymers based on N‐substituted maleimides

Physicochemical and functional properties of 2,2‐diallyl‐1,1,3,3‐tetraethylguanidinium chloride copolymers with N‐(n‐carboxyphenyl)maleimide, of N‐vinylpyrrolidone with N‐(n‐carboxyphenyl)maleimide, and of N‐vinylpyrrolidone with N‐phenylmaleimide have been investigated. Specific surface area and porosity of the copolymers under investigation have been determined by using the low‐temperature adsorption method. Electron microscope investigations in surfaces of the polymers have evinced that all of them have a spongy microstructure, the N‐vinylpyrrolidone copolymer with N‐(n‐carboxyphenyl)maleimide being the most homogeneous of these. Sorption capacity of the copolymers toward Re(VII) ions has been investigated. The process is described by the Langmuir isotherm. The pH is the most important parameter for sorption process of Re(VII). In the conjoint presence of Re(VII) and Mo(VI) in a solution of acid and ammoniac mediums, rhenium can be separated from molybdenum by using the sorbents under investigation at pH > 4.5 or at hydrochloric acid concentrations 0.1 mol L^?1 and more. © 2013 Wiley Periodicals, Inc. J. Appl. Polym. Sci., 2013     

Strain-induced crystallization kinetics of vinylidene chloride/vinyl chloride (VDC/VC) copolymers

The strain-induced crystallization (SIC) behavior of VDC/VC copolymers has a significant effect on processibility on the blown film process. However, data on SIC of VCD/VC copolymers has been very limited due to the difficulty of measuring the rapid crystallization rates induced by strain; whereas, crystallization under quiescent conditions has been studied extensively. In this work, SIC of VDC/VC copolymers has been calculated from measurements of the adiabatic temperature rise upon stretching of amorphous specimens. The effect of stretching conditions such as strain rate, total strain, and initial temperature and the effect of polymer variables such as copolymer composition, molecular weight, and plasticizer content are determined. It is found that the performance of different VDC/VC copolymers on the film-blowing process correlates much better with measurements of SIC than with quiescent crystallization behavior.     

Synthesis and solid‐state properties of crosslinked alternating copolymers of phenyl vinylethylene carbonate and N‐substituted maleimides

The copolymers of phenyl vinylethylene carbonate (PVEC) and N‐phenylmaleimide were prepared with various monomer feeds by using a radical initiator. These copolymers were crosslinked by aminolysis between hexamethylenediamine (HMDA) and cyclic carbonate moiety in the side‐chain to obtain the networked polymers having the hydroxyurethane structure. Furthermore, the crosslinked copolymers having the polar cyclic carbonate in the side‐chain were synthesized from PVEC and several bifunctional maleimides, and their double networked polymers were prepared with HMDA. These copolymers and networked polymers exhibited color changes depending on their structures based on the acid–base switching in the solid‐state. © 2017 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2017 , 134, 45247.     

Homopolymerization and copolymerization of N‐substituted maleimides with chiral anionic initiators

Novel optically active anionic initiators bearing a chiral oxazole substituent on the fluorene ring, (S)‐1‐(9H‐fluoren‐2‐yl)‐4‐isopropyl‐4,5‐dihydrooxazole lithium (Li‐(S)‐1‐FIDH) and (S)‐2‐(9H‐fluoren‐2‐yl)‐4‐isopropyl‐4,5‐dihydrooxazole lithium (Li‐(S)‐2‐FIDH), were prepared. Anionic homopolymerizations of achiral N‐substituted maleimide (RMI) with the chiral initiators were investigated. The optically active polymers obtained were attributed to asymmetric induction of the chiral initiators. The very crowded chiral initiator Li‐(S)‐1‐FIDH was found to play a better asymmetric induction role in the polymers than Li‐(S)‐2‐FIDH. Anionic copolymerization of (R)‐(+)‐N‐1‐phenylethyl maleimide and optically inactive RMI with Li‐(S)‐1‐FIDH were also studied. © 2014 Society of Chemical Industry     

Triblock copolymers of methyl methacrylate/N‐vinyl pyrrolidone and their hydrophilication effects on poly(vinylidene fluoride) porous membranes

The new amphiphilic triblock copolymers of poly(N‐vinyl pyrrolidone‐b‐methyl methacrylate‐b‐N‐vinyl pyrrolidone) (P(VP‐b‐MMA‐b‐VP)) were synthesized via a reversible addition fragmentation chain transfer polymerization route. Using these copolymers as additives in casting solutions, the porous blend membranes of poly (vinylidene fluoride) and P(VP‐b‐MMA‐b‐VP) were prepared following a typical nonsolvent induced phase separation process. The influences of P(VP‐b‐MMA‐b‐VP) on the morphologies of the blend membranes were observed by scanning electron microscopy. The chemical compositions in membrane surface layers were measured by X‐ray photoelectron measurement. Water contact angle and water flux experiments were used to evaluate the hydrophilicity and permeation properties of the blend membranes. It was found that the P(VP‐b‐MMA‐b‐VP) copolymers could be retained in membrane stably in membrane formation and application process. The copolymers could enrich in surface layer and endowed the blend membrane with efficient hydrophilicity and higher water permeation flux. © 2010 Wiley Periodicals, Inc. J Appl Polym Sci, 2010     

氯乙烯-偏氯乙烯共聚乳液的生产与应用

叙述了乳液聚合技术的发展历程及共聚乳液的反应机制,介绍了氯乙烯-偏氯乙烯共聚乳液的基础配方及生产方法,指出影响乳液质量的关键因素是单体质量、乳化剂质量及其配比。     

Stabilization of poly(vinyl chloride) against photo‐degradation using dienophilic compounds

As dienophilic compounds, N‐ aminophenylmaleimides would be expected to act as radical traps and thus, could be investigated as organic photo‐stabilizers for rigid poly(vinyl chloride) (PVC). Their stabilizing efficiencies were evaluated by measuring the extent of discoloration and the change in the mechanical properties of the photo‐irradiated polymer. Their stabilizing efficiencies were compared with phenyl salicylate, which is a commonly used industrial photo stabilizer. The results have proved the higher stabilizing efficiency of all the investigated materials as compared with phenyl salicylate. The stabilizing efficiency of the aminomaleimides is attributed to their radical trapping potency which intervenes with the radical degradation of the photo‐irradiated PVC. Moreover, it was found that these materials lower the extent of discoloration of the polymer during later stages of degradation. This improvement in the color stability is most probably attributable to the ability of the aminomalemides to react by a Diels–Alder reaction with the conjugated double bonds created on the polymeric chains as a result of the degradation of the polymer. Finally, the results illustrate the blending of aminomaleimide derivatives with phenyl salicylate improve the photo stabilization of the polymer as shown from the absorbance coefficient Δa values, and this improvement attains its maximum when both the investigated stabilizers and phenyl salicylate are taken in equivalent ratios. The observed synergism is attributed to the combination of the mechanisms by which both stabilizers function. © 2009 Wiley Periodicals, Inc. J Appl Polym Sci, 2009     

Use of N‐(N′‐arylamino)maleimides to improve the thermal properties of poly(vinyl chloride) through chemical modification and graft copolymerization

The reaction of poly(vinyl chloride) (PVC) with N‐(N′‐arylamino)maleimide derivatives was studied. The thermal stability of the modified polymer was improved markedly when compared with that of the unmodified polymer. The stability improvement was attributed to the replacement of the labile chlorine atoms by more stable organic groups. The modified polymer also showed a lower extent of discoloration when compared with that of unmodified PVC. In order to introduce a polymeric stabilizer into PVC, the dienophilic monomer was chemically grafted onto the polymeric chains. The mechanism of the chemical modification as well as that of the graft copolymerization are discussed. J. VINYL ADDIT. TECHNOL., 2008. © 2008 Society of Plastics Engineers.     

Shear degradation of vinylidene chloride copolymers

Thermally induced dehydrochlorination is a well-established and prominent degradation mode for vinylidene chloride copolymers. During extrusion, other processes may represent significant degradation pathways. Under shear in air, both oxidative chain-scission and cross-linking are prominent processes for both vinylidene chloride/vinyl chloride and vinylidene chloride/methyl acrylate copolymers. Both processes are dependent upon shear rate and temperature. The shear-stress dependency can be modeled by a kinetic expression that incorporates shear stress into the Arrhenius preexponential factor. Vinylidene chloride/methyl acrylate copolymers appear to be somewhat more susceptible to oxidative chain-scission than are comparable vinylidene chloride/vinyl chloride copolymers, presumably because of a rapid oxidative attack at exposed methyl acrylate units. Shear-induced degradation of these materials in air is characterized by early predominant chain-scission with cross-linking assuming a greater importance as a function of time. Degradation under shear in a nonoxidative environment is a much simpler process—oxidative chain-scission is suppressed and cross-linking is very similar to that observed in air. © 1994 John Wiley & Sons, Inc.     

Thermal and photodegradation of vinyl chloride/vinyl bromide copolymers

Vinyl chloride/vinyl bromide (VC/VBr) copolymers have been synthesized by radical copolymerization in bulk. Conversion increases and molecular weight of the copolymers decreases with increasing VBr in the feed. This indicates that VBr is a chain transfer agent in VC/VBr copolymerization systems. In accordance with the lower thermal stability of the vinylbromide homopolymer (PVBr), thermal degradation experiments show that the stability of the copolymers significantly decreases with increasing VBr content. It has been found that the initial rate of dehydrohalogenation is an exponential function of VBr content during thermal degradation of VC/VBr copolymers. In separate experiments, HBr evolved during degradation has been determined by a bromide selective electrode. The initial dehydrobromination rates of VC/VBr copolymers containing higher fractions of VBr are markedly higher than the initial dehydrochlorination rates. This clearly indicates the lower thermal stability of VBr monomer units compared with VC units. UV and visible spectra of degraded VC/VBr copolymers show that the absorption and the average length of polyenes are higher for samples with higher VBr content. Dehydrohalogenation curves obtained during photodegradation of VC/VBr copolymers show a faster initial phase followed by a slower stationary phase. The initial rate of dehydrohalogenation is higher for copolymers containing higher fractions of VBr, whereas these copolymers reach the slower stationary phases at lower extents of dehydrohalogenation.     

Strain-induced crystallization kinetics of vinylidene chloride/vinyl chloride (VDC/VC) copolymers. Part II. Effect of temperature

The strain-induced crystallization (SIC) behavior of vinylidene chloride/vinyl chloride (VDC/VC) copolymer is reported as a function of the uniaxial extension ratio and the temperature of the rubbery amorphous specimen. The copolymer studied was an 88/12 wt/wt VDC/VC copolymer with a weight average molecular weight of 100,000 containing liquid additives that function as processing aids. It was found that SIC is initiated at an extension ratio of approximately 3.5, independent of the stress and stretching temperature. The growth rate of the crystalline phase increases sharply with extension ratio above 3.5. The crystalline phase growth rate at a given extension ratio also increases sharply with temperature between 15°C and 35°C. The implications of film temperature control during bubble expansion on the blown film process are discussed.     

Microstructure analysis of N‐vinyl‐2‐pyrrolidone/vinyl acetate copolymers by NMR spectroscopy

N‐Vinyl‐2‐pyrrolidone (V) and vinyl acetate (A) copolymers of different compositions were synthesized by free radical bulk polymerization. The copolymer composition of these copolymers was determined using quantitative ¹³C{¹H} NMR spectra. The reactivity ratios for these comonomers were determined using the Kelen–Tudos (KT) and non‐linear least‐square error‐in‐variable (EVM) methods. The reactivity ratios calculated from the KT and EVM methods are r_V = 2.86 ± 0.16, r_A = 0.36 ± 0.09 and r_V = 2.56, r_A = 0.33, respectively. ¹H, ¹³C{¹H} and ¹H–¹³C heteronuclear shift correlation spectroscopy (HSQC) and ¹H–¹H homonuclear total correlation spectroscopy (TOCSY) were used for the compositional and configurational assignments of V/A copolymers. The ¹³C distortionless enhancement by polarization transfer (DEPT) technique was used to resolve the methine, methylene and methyl resonance signals in the V/A copolymers. © 2002 Society of Chemical Industry     

Conventional and RAFT radical copolymerizations of β‐pinene with N‐substituted maleimides

The feasibility of the radical copolymerizations of β‐pinene with three N‐substituted maleimides, i.e. N‐phenylmaleimide (PhMI), N‐methylmaleimide (MeMI), and N‐ethylmaleimide (EtMI), was clarified for the first time. The copolymerization rates decreased in the order PhMI > MeMI > EtMI. A marked penultimate effect on the activity of the N‐substituted maleimide‐terminated radicals was found in these copolymerizations. The penultimate monomer reactivity ratios evaluated by the nonlinear method were r₁ = 0.10, r′₁ = 8.30, r₂ = r′₂ = 0 for PhMI–β‐pinene, r₁ = 0.20, r′₁ = 7.09, r₂ = r′₂ = 0 for MeMI–β‐pinene, and r₁ = 0.16, r′₁ = 6.50, r₂ = r′₂ = 0 for EtMI–β‐pinene. Furthermore, the possible controlled copolymerizations of β‐pinene and N‐substituted maleimides were then attempted via the reversible addition‐fragmentation chain transfer (RAFT) technique. In the presence of RAFT agent 1‐phenylethyl phenyldithioacetate, the copolymerization of β‐pinene with MeMI or EtMI was retarded severely. However, much smaller retardation was observed in the RAFT copolymerization of β‐pinene with PhMI, and, more importantly, the copolymerization exhibited typical features of a controlled system. The solvent effect on the RAFT copolymerization of β‐pinene and PhMI was also investigated using matrix‐assisted laser desorption ionization time‐of‐fight mass spectrometry (MALDI‐TOF‐MS) analysis. The results clearly indicated that copolymerization in tetrahydrofuran suffered from competitive transfer and termination side‐reactions arising from the solvent in spite of the presence of the RAFT agent. Copyright © 2007 Society of Chemical Industry     

Physical properties of poly(vinyl chloride)–grafted N‐isopropylacrylamide graft copolymers and corresponding polyblends

The physical properties of poly(vinyl chloride) (PVC) and poly(N‐isopropylacrylamide) [poly(NIPAAm)] blend systems, and their corresponding graft copolymers such as PVC‐g‐NIPAAm, were investigated in this work. The compatible range for PVC–poly(NIPAAm) blend systems is less than 15 wt % poly(NIPAAm). The water absorbencies for the grafted films increase with increase in graft percentage. The water absorbencies for the blend systems increase with increase in poly(NIPAAm) content within the compatible range for the blends, but the absorbencies decrease when the amount of poly(NIPAAm) is more than the compatible range in the blend system. The tensile strengths for the graft copolymers are larger than the corresponding blends. © 2000 John Wiley & Sons, Inc. J Appl Polym Sci 76: 170–178, 2000     

Melt rheology of vinylidene chloride-vinyl chloride copolymers

A continuous extruder slit-die rheometer system determines the rheological properties of thermally sensitive copolymers of vinylidene chloride and vinyl chloride to aid the design of processing screws, melt dies, and coextrusion feed blocks for the production of barrier film. The flow of VDC-VC copolymers was dependent on molecular weight, temperature, and shear rate. Increased chain mobility causes low-melting-temperature copolymers to flow more easily. Liquid additives also reduce viscosity.     

Miscible blends of a vinylidene chloride/vinyl chloride copolymer with aliphatic polyesters

A copolymer of vinylidene chloride and vinyl chloride containing 13.5% by weight of the latter has been solution blended with four aliphatic polyesters: poly(?-caprolactone), poly(2,2-dimethyl-1,3-propylene adipate), poly(1,4-cyclohexanedimethylene succinate), and poly(2,2-dimethyl-1,3-propylene succinate). Each blend was examined visually and by differential scanning calorimetry. All blends with the copolymer form a single miscible amorphous phase at all compositions and all temperatures except for the latter mentioned polyester, which exhibits liquid–liquid phase separation at temperatures above a measured cloud point curve. Information about interactions between the components in each blend is estimated from melting point data and discussed.     

Studies on the microstructure of vinyl/N‐phenylmaleimide copolymers by NMR and their applications

The micro‐ and stereostructures and sequence distribution of methyl methacrylate (MMA)/N‐phenylmaleimide (PMI) and styrene (St)–PMI copolymers were studied in detail with NMR spectroscopy. The MMA–PMI copolymer was in a random sequence distribution and the St–PMI copolymer was alternating in structure. Some micro‐ and stereoinformation of the MMA–PMI copolymers could be obtained from ¹H‐NMR spectra. The average number sequence length obtained from the copolymer triad by ¹³C‐NMR spectra was in agreement with that calculated from the reactivity ratios measured by an elemental analyzer. From the triad fraction of the copolymer measured by ¹³C‐NMR, the copolymer chain of MMA–PMI was proved to be a one‐order Markov chain. More suitable propagation reactions were proposed from the deviation of sequence distribution of the St–PMI copolymer. © 2000 John Wiley & Sons, Inc. J Appl Polym Sci 77: 2581–2587, 2000     

Microstructure analysis of poly(styrene‐co‐vinylidene chloride) copolymers by NMR spectroscopy

Poly(styrene‐co‐vinylidene chloride) (S/V) copolymers were prepared by free‐radical photopolymerization using uranyl nitrate as an initiator. The microstructure of the copolymer S/V was investigated by ¹H‐ and ¹³C{¹H}‐NMR, ¹H–¹³C‐heteronuclear shift quantum correlation (HSQC) NMR, and homonuclear total correlated spectroscopy (TOCSY). The ¹H‐NMR spectra of the copolymers is complex due to overlapping resonance signals of the various triad configurations. Assignments were made up to the triad and tetrad levels for the methylene and methine regions using two‐dimensional HSQC experiments. A ¹³C‐distortionless enhancement by polarization transfer (DEPT) spectrum was used to differentiate between the carbon resonance signals of methine and the methylene units. The geminal couplings in the methylene protons and vicinal coupling between the methine and methylene protons were detected from the TOCSY spectra. Monte Carlo simulations were used to investigate the effect of the degree of polymerization on the triad fractions. © 2000 John Wiley & Sons, Inc. J Appl Polym Sci 79: 544–554, 2001     

Preparation and thermal and thermo‐oxidative stability of vinylidene chloride‐co‐vinyl chloride copolymer/synthetic hectorite nanocomposites

Poly(vinylidene chloride‐co‐vinylchloride)/organically modified hectorite (VDC‐VC/SPN) nanocomposites were prepared by melt blending VDC‐VC copolymer with SPN in the presence of dioctyl phthalate, which acted as a plasticizer. As a result, the exfoliated structure was found in the VDC‐VC/SPN nanocomposites. In nitrogen atmosphere, VDC‐VC/SPN nanocomposites exhibited a single‐step thermal degradation. The thermal stability of VDC‐VC/SPN nanocomposites is significantly influenced by the SPN, which was modified with long alkyl ternary ammonium salt. In air atmosphere, VDC‐VC/SPN nanocomposites revealed a two‐step thermo‐oxidative degradation behavior. At the first degradation stage, the weight loss pattern is similar to that of VDC‐VC composites in nitrogen, in which the thermo‐oxidative stability of VDC‐VC/SPN nanocomposites is affected by the ternary ammonium salt and oxygen rather than its morphology. At the second degradation stage, both the enhanced thermo‐oxidative stability and the flame‐retardation ability of VDC‐VC composites are strongly and closely related to the morphology of nanocomposites. © 2009 Wiley Periodicals, Inc. J Appl Polym Sci ,2009