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The influence of irradiation parameters,such as the irradiation time,temperature and the acrylate functionality of monomers on the infrared laser induced photopolymerization were investigated in this paper. A novel cationic cyanine dye-borate complex, 1,3, 3, 1', 3', 3'-hexamethyl-ll-chloro-10, 12-propylene-tricarbocyanine triphenylbutylborate, was employed as the photoinitiator. It had maximum absorption wavelength lambda (max) at 780 nm in 2-butanone with the maximum molar extinction coefficient epsilon (max) of 1.4 x 10(5) L . mol(-1). cm(-1), which matched well with the emitting wavelength, 796 nm,of the adopted infrared laser diode. With poly(vinyl alcohol)(PVA) as oxygen barrier layer, photopolymerization system containing trihydroxymethylpropanetriacrylate(TMPTA), binder and photoinitiator was cured by 2 min of infrared laser irradiation. Modest improvement of the double-bond conversion could be achieved by increasing the irradiation time or temperature. Furthermore,it was found that the monomer with diacrylate functionality had higher double-bond conversion than that with triacrylate functionality under the same irradiation conditions. Double-bond: conversion of 52% could be achieved for diacrylate monomer phthalic diglycol diacrylate(PDDA) compared with 25% for triacrylate monomer TMPTA.
Two stilbene-containing polyethers (PSEG, PSV) were synthesized and their thermotropic liquid crystalline behavior was investigated. The respective backbone polymers, poly(-glycidyl 2-chloroethyl ether),P(GCE),and poly(glycidyl 2-chloroethyl ether)-co-4-hydroxybutyl vinyl ether),P(GCE-co HBVE),were prepared by cationic polymerization and photo copolymerization respectively. Liquid crystal polyether PSEG,PSV were synthesized through the macromolecular reaction of P(GCE) and P(GCE-co-HBVE) with 4-nitro-4/-hydroxy stilbene (NHS) respectively. The chemical structures and chromophore contents of these polyethers were characterized by means of FTIR,H-1-NMR and EA. The phase transition temperature, texture structure,thermal stability and phase behavior were investigated by POM,DSC,TGA and WAXD, The results showed that these polyethers were nematic bitropic liquid crystals with low and wide phase transition temperatures,as well as good thermal stability.
Dynamic viscoelasticity of curvielan, a novel gel-forming exopolysaccharide produced by soil bacterium Alcaligenes sp.Q9415 was studied. Over the angular frequency (omega) range 0.01 similar to 100rad .s(-1), the storage modulus (G') of 1.4% (W/W) curvielan gels was much higher than its loss modulus (G ") and less dependent on frequency which showed that curvielan had fine elasticity. 0.5% was close to the threshold concentration needed for gelation. Curvielan was dispersible in cold water to form weak gel which could become much strong viscoelastic gel at about 90 degreesC for 10min. Continuous heating at high temperature and freezing-thawing treatment damaged the network of curvielan gel. Similar results were observed for curvielan gels prepared under pH 3 and 10. Addition of 1% similar to 18 % NaCl, 6 % KCl, CaCl2, MgCl2, ZnCl2 and 20% sucrose decreased the G' of 1% curvielan gel at low frequency and increased G " over the frequency range 0.01 similar to 100rad .s(-1) which indicated that the formation of elastic network was hindered, However, addition of 6% AlCl3 of FeCl3 made total loss of viscoelasticity of the 1% curvielan system.
The resistivity of the conductive composite varies as a function of the volume fraction of the conductive material. Considerable experimental and theoretical work has been done to examine how the volume fractions and the morphology of the components affect the electrical behavior of the composite materials. The generalized effective medium(GEM) equation gives the complete information on how the volume fraction of components may affect the medium conductivity by taking into an account the intrinsic conductivities and geometries of both components and also their arrangement and orientation in the applied electric fields. In this paper the electrical percolation phenomenon in CB/HDPE composite influenced by crosslinking under different irradiation doses and different ambient temperatures has been investigated, The experimental data regarding the dependence of conductivity on the volume fraction of CB were fitted into the GEM equation. The parameters in the GEM equation, corresponding to the dispersion characters of CB in HDPE matrix,were determined through the computer fitting. The CB particles aggregated constructing a three-dimensional conducting network along the electrical current direction. The polymer matrix,however,is statistically vertical to electrical current direction, hindering conductive particles from contacting each other. The higher the irradiation dose or the ambient temperature, the more serious the hindrance. The electrical conductivity of HDPE composites filled with high-structure CB particles is dominated by percolation mechanism based on a particle-touching model, while crosslinking or ambient temperature increasing causes a larger gap between the conductive particles and makes the conductivity more affected by tunneling mechanism.
Pyrene was used as a fluorescent probe to investigate the polarity and stability of the micelle of anionic aqueous polyurethane dispersion(AAPUD). Results indicated that the micelle is non-polar or weak polar,and the polarity is greatly dependent on the hydrophilicity of the main chain of polyurethane and the pH value of the medium. The polarized value of the polarized fluorescent of pyrene in the AAPUD was measured, and the results show that the stability of the micelle could be characterized by the polarized value.
The DR-PPA polyelectrolyte complex was formed via the interaction of diazoresin (DR) and polyphosphoric acid (PPA) in aqueous solution. The DR-PPA complex does not dissolve in water but dissolves considerably in sodium dodecyl sulfate(SDS)aqueous solution. The solubility of DR-PPA in 0.05, 0.10,0.15 mol/L SDS aqueous solution(100 mL) was determined at 20°C to be 0.25, 1.10 and 1.80 g respectively. The DR-PPA/SDS film on a substrate (modified PET film or anodized Al plate) is photosensitive and can produce an image under the exposure of UV light through a photographic film. The photodecomposition of DR-PPA in 0.15 mol/L SDS aqueous solution or in its solid film was carried out and confirmed to be, both in solution and in film,in accordance with the first order reaction in kinetics. An ultrathin multilayer film from DR and PPA has been prepared by self-assembly technique. It was verified that the self-assembly process progresses smoothly with an absorbance increasing of °0.02 per DR-PPA layer at 370nm. The multilayer film is also photosensitive and its decomposition is also in agreement well with first order reaction. Under UV irradiation the ionic bond both in the coating and in self-assembly films converts to covalent bond. As a result the dissolution behavior of the DR-PPA film changes dramatically i.e. from soluble in SDS aqueous solution to insoluble because the crosslinking nature of the film changes from ionic before irradiation to covalent after irradiation.
Polyphenylene sulfide (PPS)/polyamide 6 (PA6) blends were prepared by different methods including melting-, powder- and powder-solution-blendings. Ef:ect, of interface interaction on the crystallization behavior of PPS and PA6 componens in these blends were investigated by components differential scanning calorimetry under nonisothermal conditions. The results indicate that the crystallization temperatures for PPS are shifted to a greater extent than those for PA6 in the blends. The PPS and PA6 both crystallize at higher temperatures as a result of blending. The crystallization temperatures of PP in its blends are always higher than that of pure PPS and are independent of the method of preparation. The order of increase in the crystallization temperatures of PPS is melt-blends >powder-solution-blends> powder-blends. The PPS crystallization peak becomes narrower and the crystallization temperature shifts to a higher temperature; suggesting a faster rate of crystallization as a result of blending with PA6. This enhancement in nucleation of PPS could be attributed to the possible effect of interfacial interaction between the component polymers in inducing heterogeneous nucleation.
The compatibility of components, melting and crystallization behavior as well as degradations of blends for maleated LLDPE(MPE)/poly( e \|caprolactone)\|poly(oxyethylene) copolymer(PCE)have been investigated by vibrating reed, DSC and FTIR. The degradations are characterized by the retention of tensile properties.The results show that the maleation reaction occurs at the methyl end group of the short\|chain branching of LLDPE, resulting hydrogen interaction between maleic anhydride and hydroxyl group of PCE. This type of the interaction causes a partial compatibility between the blend components, as indicated by an inward shifting of the glass transition of PCE and β transition of MPE. Introduction of ethyl\|acrylic acid copolymer(EAA)in the blends further depresses the melting point, reduces the melting enthalpy and enhances the compatibility of components. The photo\| and hydrolytic degradations of MPE/EAA/PCE blends increase with PCE content. The rate of a combination of the photo\|hydrolytic degradation is more rapid than that of the individual degradations of photo\| or hydrolytic nature.
The orientational order of a liquid crystalline( LC)system is in favor of the alignment of nonlinear optical (NLO) units. If a NLO unit is:also a LC unit, the resulted liquid crystalline NLO polymer may possess a higher orientational order and therefore promote the nonlinear optical sensibility. A polymalonate side chain liquid crystalline (LC) polymer with a nonlinear optical nitro azobenzene type mesogenic unit has been synthesized by melt polycondensation, which was characterized by FTIR and H-1-NMR. The thermal transition temperatures and LC properties of the polymer were determined by DSC, polarized optical microscope(POM) and WAXD. A typical-smectic focal conic texture was observed under POM and two small sharp WAXD peaks corresponding to Bragg's spacings 2.74nm and 1.35nm appeared in the smectic phase, Moreover, spin-coating films of the polymer through corona poling possessed an orientational order parameter phi =0.33 calculated from UV measurements. But light scattering resulted from the crystallization of the polymer reduced the transparency of the polymer film and some small sharp peaks appeared in the UV spectra.
The structure changes of the industrial yam of poly(ethylene terephthalate)(PET) of 1455dTex/ 110f under the tension of 0.3N and at the temperature range of 375 similar to 494K( were characterized by WAXD, density gradient method, sonic velocity measurements,and DSC. The shrinkage could be divided into two different processes characterized by different relaxation times and final shrinkage amounts. The molecular mechanism for the first process, the fast and dominant one, mainly was the disorientation of the extended segments in the amorphous region, which can be proved by the change of orientation function of the amorphous region (f(am)) with shrinkage time at different temperatures. More meaningful thing is that the shape and change tendencies of f(am) and relative length (l(t)) with shrinkage time are very similar. The second slow one was resulted from the restructuring of the crystalline region, which included the rapid growth of the crystallites, the formation of new imperfect crystals and the reorganization of existed crystals during the whole shriknage process. The changes of crystalline regions became fast with the temperature rising and consequently their effect of restriction of the disorientation of the amorphous region became more obvious. However, the orientation function of crystalline regions keeps unchanged almost during the thermal shrinkage process. It should be indicated that the structure changes of amorphous and crystalline regions are not independently. Each process proceeds and competes each other during the thermal shriknage. The contribution of both processes to the shrinkage mainly depends on the temperature and time. The study of structure change of PET yarn during thermal shrinkage provides an important idea of developing more perfect crystalline regions to limit the thermal shrinkage due to the disorientation in amorphous regions. PET yarns with strength of 7cN/dTex, modulus of 4.4cN/dTex at 5% elongation and thermal shrinkage of 3.5% have been successfully obtained.
In literatures montmorillonite's organic modification usually use one-step intercalation method, we developed a two-step intercalation method by using two different organic salts continuously.After comparing the effects of one-step method and two-step method, we found that the effect of two-step intercalation method was much better than that of one-step method. The nanocomposites were prepared by suspension polymerization of methyl methacrylate(MMA) containing intercalated montmorillonite, and the results of their FT-IR, XRD and SEM studies proved that the montmorillonite was effectively swollen or exfoliated. Adding montmorillonite could affect the process of suspension polymerization. We found that the conversion of monomer was lowered, the shape of polymer granules was changed to be irregular, and granules' diameter was enlarged. DSC, solvency experiment and strain experiment showed that adding montmorillonite may improve the properties of PMMA because of polymer's cross-linking by montmorillonite. The best weight content of montmorillonite was about 3%.
The thermal-oxidative degrading regulation of blends containing starch, polyethylene and additives which is made up of combination of Fe3+ -oleic acid at simulating composting temperature(70 degreesC) was stdied. Sample films were made by conventional extrusion blowing. The additives and starch were introduced into the LDPE matrix in the form of masterbatchs in the amount of 10 % ( W/W) and 60 % ( W/W), respectively. Samples were put into two different degrading environments,a certain number of films were taken out after an interval of ten days for testing. The mechanical properties, viscosity-average molecular weight and hydroperoxide concentration of the samples in the matrix were measured. Moreover, the superficial conformation and crystal capability of the aged samples were also characterized by SEM and XRD. It was showed that the adopted additives could catalyze the degradation of PE efficiently. Besides,it was found that though the concentration of O-2 affected very much the degrading behavior of PE, the catalyzing efficiency of some additives,such as FS,with high content of Fe3+ was almost unaffected under low O-2 concentrations. So it was more suitable for initiating degradation of PE at real composting environment. The degrading mechanism of PE matrix was deduced according to the experimental results. The kinetics of hydroperoxide formation corresponded to an exponential law as claimed in the literature. The curve of hydroperoxide accumulation well conformed to a quadratic law in the early stage,when the progress deviated from the induction period, passed the maximum rate, and reached the limit concentration [POOH](infinity) at deceleration.
The intercalate and exfoliate actions of BHET or PEG for montmorillonite are discussed.BHET(ethylene glycol terephthalate) can be absorbed and intercalated between layers of montmorillonite, not only at high temperature, but also normal temperture.Especially at temperatures,30～40℃ over the melt temperature,more BHET are absorbed by montmorillonite.When the content of montmorillonite is less than 10% in its mixture with BHET the stack layers of montmorillonite can be exfoliated into single layers.But when the content of montmorillonite is more than 10% a few exfoliated layers combined into more layers.Montmorillonites can also absorb PEG,but in this case only the layer distances are increased,no layer exfoliation is observed.Between the layers one to three layers of PEG molecules can be absorbed.So that,there are respectively three peaks d =4 4,3 4 and 1 8nm in WAXD curves.When the content of montmorillonite is more than 10% there is only one layer distance d =1 8nm.
The effects of esterification with stearic acid on the crystallizing behavior,thermal stability and resistance to water of polyvinyl alcohol(PVA) were studied by using IR, WAXD, DSC, TG and water resistance test. The results show that the esterification of PVA with stearic acid could take place in the presence of dibutyltin dilaurate at 128 degreesC.-OOC(CH2)(16)CH3 groups are introduced into PVA molecular chains during esterification. With increasing the reaction time, the thermal stability and water resistance of PVA are improved. However, the crystallinity and melting temperature of PVA are decreased. As reaction time exceeds 16h, the crystalline structure of PVA disappears according to WAXD and DSC curves. The initial decomposition temperature after esterification is over 200 degreesC,much higher than that of PVA. These results suggest a method for improving the thermal stability and water resistance of PVA.
Poly(vinyl alcohol) (PVA) and two ethylene-vinyl alcohol copolymers were esterified with undecenoyl chloride and a mixture of undecenoyl and benzoyl chlorides to test how the double bond content and aromatic or aliphatic spacers can affect the further crosslinking reaction. In all cases crosslinking was only possible by using a peroxide initiator to prevent simultaneous thermal degradation. Isoconversional kinetic analysis was applied to dynamic DSC data. This study reveals the complexity of the crosslinking process because the activation energy depends on the conversion degree. In the polymers which contain most double bonds, diffusion is the rate limiting step at high conversion. As a general trend, E a values increase when the number of double bonds decreases. However, when there are many benzoate moieties, E a values are lower probably due to the more expanded conformation that the random coil must adopted.
Monocyclic monomers bearing exo-methylene groups are likely to undergo ring-opening polymerization under the conditions of radical or cationic initiation. Several structural features will determine the course of reaction after initiation by species that exclusively attack the exo-methylene functionality. Reviewing some of the most common classes of monocyclic heterocycles it becomes obvious that a monomer has to meet certain structural preconditions that makes them suitable for isomerizations. Among the considered heterocycles there are some types of monomers possessing an outstanding ring-opening behavior following polymerization mechanisms free from side-reactions. The combination of strain release due to ring-opening isomerization, an energy decrease in the transition state caused by the formation of carbonyl-functionalities and an appropriate stabilization of the growing chain end by steric and electronic effects may lead to clear ring-opening mechanisms. However, this property remains restricted to only some special monomers with simple aromatic substituents being attached to the cycle. Hence a variety of cyclic ketene acetals, enolethers, (meth)acrylates, carbonates, lactones and lactames have been chosen in order too demonstrate both the possibilities and limits of ring-opening.
Different syntheses of ordered condensation polymers from nonsymmetric monomers are reviewed. For several classes of polymers, the approach exploiting reactivity differences between the functional groups of the nonsymmetric monomers (ordered polymers from in situ generated intermediates) is compared with that where the relevant intermediates are used as symmetrical preformed and/or isolated precursors for the ordered polymers.
The retardation time spectra in the glass transition range are discussed on hand of multidimensional deuteron NMR experiments, measurements of the dielectric loss and the T1-relaxation of proton spins in liquids at different temperatures and different frequencies. The data can be described by applying the model of reversible aggregation. Every liquid is here characterized by a broad aggregate size distribution. Relaxation is interpreted as collective response of intra-aggregate Debye processes running off while the aggregate ensemble fluctuates. The relaxation time increases with the volume of the aggregate so that every relaxation time distribution is strictly related to the aggregate size distribution. The shape of relaxation mode distributions is similar, the width depends on how the molecular mechanisms couple to the stationary dynamics. The coupling changes on heating so that the width of the relaxation mode distribution decreases. A full description of the α-process needs to account for aggregate ensemble fluctuations, a bimodal relaxation mode spectrum and a heterogeneous kinetics.
The nucleophilic substitution reactions on poly(vinyl chloride) (PVC) with sodium benzenethiolate, sodium thiobenzoate and sodium 2-mercaptobenzothiazolate have been carried out in solution of cyclohexanone. The aim was to study from a comparative point of view the influence of nucleophile characteristics, in particular bulkiness, on the reaction mechanisms through the microstructural evolution with degree of substitution of the same PVC sample with the three kinds of nucleophile in the same experimental conditions. The quantitative microstructural analysis with conversion has been followed by 13C NMR spectroscopy. Owing to steric hindrance of 2-mercaptobenzenethiolate the stereoselective nature of the reaction is enhanced making the reaction through the mr triads of mmr inoperative in practice unlike the other nucleophiles. This conclusion was confirmed on the basis of the FTIR results.
