SA-AA-MA聚合物的合成及阻垢分散性能

以苯乙烯磺酸钠(SA)、丙烯酸(AA)、丙烯酸甲酯(MA)为单体,采用正交设计方法,通过其对碳酸钙和磷酸钙的阻垢性能,确定AA-SA-MA聚合物的最佳合成比例,即n(苯乙烯磺酸钠)∶n(丙烯酸)∶n(丙烯酸甲酯)=1.5∶5.0∶1.0,引发剂的质量分数为4%,并对合成的AA-SA-MA进行阻垢分散性能进行了评价,结果表明合成的AA-SA-MA聚合物具有优良的综合性能。     

Polyaldehydes: homopolymers,block copolymers and promising applications

This minireview gives a brief overview on the polymerization of higher aldehydes, discusses current applications of certain polyaldehydes, and points toward potential future applications of these interesting materials. Although it was discovered long ago that several aldehydes can be polymerized, the application potential of these polymers was largely overlooked. This is somewhat surprising as many polyaldehydes show interesting properties such as fast and complete depolymerization triggered by chemical or thermal stimuli. Such stimuli‐responsive polymers can be useful materials in many applications in for example nanotechnology or drug delivery. By incorporating polyaldehydes into functional block copolymers even more versatile materials can be created. The increasing number of recent research examples demonstrates the growing interest in polyaldehydes as smart materials and their potential for novel applications. Copyright © 2012 Society of Chemical Industry     

Dynamic mechanical and rheological properties of metallocene-catalyzed long-chain-branched ethylene/propylene copolymers

The dynamic mechanical and rheological properties of five long-chain branched (LCB) and three linear ethylene/propylene (EP) copolymers were investigated and compared using a dynamic mechanical analyzer (DMA) and an oscillatory rheometer. The novel series of LCB EP copolymers were synthesized with a constrained geometry catalyst (CGC), [C₅Me₄(SiMe₂N^tBu)]TiMe₂, and had various propylene molar fractions of 0.01-0.11 and long-chain branch frequencies (LCBF) of 0.05-0.22. The linear EP copolymers were synthesized with an ansa-zirconocene catalyst, rac-Et(Ind)₂ZrCl₂ (EBI), and contained similar levels of propylene incorporation as the CGC copolymers, but no LCB. In dynamic mechanical analysis, the dynamic storage moduli (G′) and loss moduli (G″) of the copolymers decreased with an increase of propylene molar fraction. The α- and β-transitions of the CGC copolymers were overlaid with each other. High damping (tan δ) values were found with the CGC copolymers at temperatures below 0 °C. In oscillatory rheological analysis, compared to the linear EBI counterparts, the LCB CGC copolymer melts showed higher zero shear activation energies, broader plateaus of δ and larger elastic contributions, which are essential characteristics of LCB polymers. It was found that the long chain branching was the determining factor in controlling rheological properties of the polymer melts while the short chain branching from propylene incorporation played a decisive role in affecting dynamic mechanical properties. This work represents the first rheological evidence of LCB in EP copolymers synthesized with CGC.     

Effects and measurements of polyoxyethylene block length in polyoxyethylene-polyoxybutylene copolymers

Block copolymer surfactants, made from 1,2-butylene oxide (BO), propylene oxide (PO) and ethylene oxide (EO), exhibit wide ranges of properties and performance. In particular, BO/EO block copolymers exhibit improved surfactant performance with respect to PO/EO analogs. One interesting difference between these two classes of surfactants is the EO capping efficiency of polyoxypropylene (POP) vs. polyoxybutylene (POB) hydrophobe secondary hydroxyl groups. In this regard, nuclear magnetic resonance measurements have shown that POP secondary diols react more readily with EO than POB diols. For the case of ethoxylated POB polymers, the amount of unethoxylated secondary hydroxyl is proportional to the average length of the polyoxyethylene (POE) blocks. Differential scanning calorimetry was used to observe crystallinity of POE blocks. For a given POB hydrophobe molecular weight and weight percentage EO, surfactant performance properties can be augmented by affecting POE block length in the ethoxylation process.     

A new approach for the prediction of ash fusion temperatures: A case study using Turkish lignites

Prediction of ash fusion temperatures by using the chemical composition of the ash has previously been conducted only with linear correlations. In this study, a new technique is presented for predicting the fusibility temperatures of ash. Non-linear correlations are developed by using the chemical composition of ash (eight oxides) and coal parameters (ash content, specific gravity, Hardgrove index and mineral matter content). Regression analyses are conducted using information for Turkish lignites. Regression coefficients and variances of non-linear and linear correlations are compared. The results show that the non-linear correlations are superior to linear correlations for estimating ash fusion temperatures.     

Synthesis of poly(trioctylammonium p-styrenesulfonate) homopolymers and block copolymers by RAFT polymerization

A method to prepare sulfonated polystyrene-containing block copolymers has been investigated by neutralizing styrene sulfonic acid with trioctylamine to produce the hydrophobic monomer trioctylammonium p-styrenesulfonate (SS-TOA). This monomer was polymerized by reversible addition fragmentation chain transfer (RAFT) polymerization to produce PSS-TOA homopolymers. A PSS-TOA homopolymer was then used as a macro-RAFT agent for the polymerization of styrene to prepare poly(trioctylammonium p-styrenesulfonate)-block-poly(styrene) (PSS-TOA-b-PS). These block copolymers could be ion-exchanged to produce either the hydrophilic sodium salt form of PSS or a hydrophobic quaternary ammonium salt. This approach will be useful for preparing PSS-containing block copolymers with a range of hydrophobic blocks for applications such as ion-exchange membranes.     

Controlled synthesis of vinyl-functionalized homopolymers and block copolymers by RAFT polymerization of vinyl methacrylate

Reversible addition-fragmentation chain transfer (RAFT) polymerization of an asymmetrical divinyl monomer, vinyl methacrylate (VMA), was investigated under various conditions. RAFT polymerization of VMA using a dithioester-type chain transfer agent (CTA) under suitable conditions afforded soluble polymers with a high content of pendant vinyl ester side chains in sufficient yields (>70%). The monomer concentration, the nature of the CTA, and the CTA/initiator ratio were found to affect the polymerization reaction and the structure of the resulting polymers; this behavior is attributed to the relative propensities for intermolecular propagating/cross-linking reactions and intramolecular cyclization. A kinetic study of the RAFT polymerization of VMA with the dithioester-type CTA 1 suggested that the propagation reaction of the methacryloyl group proceeded predominantly with a certain level of intramolecular cyclization during the early stage of the polymerization and intermolecular cross-linking during the final stage of the polymerization. Block copolymers with one segment featuring pendant vinyl functionality were synthesized by RAFT polymerization of VMA using poly(methyl methacrylate) as a macro-chain transfer agent (macro-CTA).     

Synthesis,morphology, and melting behavior of poly(ether ether ketone) of different molecular weights

To investigate how the molecular weight of poly(ether ether ketone) affected the crystallization behavior, the nucleophilic reaction synthetic technology was used to obtain poly(ether ether ketone) of different molecular weights and the trend of the molecular weight varying with the duration of the reaction. Furthermore, the influence molecular weight has brought to the morphology and the melting behavior was investigated by means of FTIR, OM, WAXD, and DSC and thoroughly discussed in theory. Results showed that with the increase of the molecular weight, the degree of crystalline perfection and the lamellar thickness descended as well as the radius of spherulite diminished due to the difficulty of the chain mobility. Moreover, the melting temperature mounted up at first then decreased with the growing of the molecular weight indicating how the lamellar thickness and the melting heat per unit volume affected the melting behavior together. © 2009 Wiley Periodicals, Inc. J Appl Polym Sci, 2009     

Effect of multifunctional comonomers on the properties of poly(ethylene terephthalate) copolymers

The properties of poly(ethylene terephthalate) (PET) and its copolymers containing 0.04–0.15 mol% of pentaerythritol and trimethylolethane (TME) have been investigated. The molecular weight of the copolymers increased with comonomer content, and this effect was observed significantly with pentaerythritol copolymers, resulting in broad molecular weight distribution. The comonomer effect on the mechanical properties was small. The shear viscosity of the copolymers showed shear thinning within the experimental shear rate range. The crystallization rate and birefringence of the fibres containing 0.103 mol% pentaerythritol increased with the spin draw ratio, whereas they decreased with comonomer content. © 2002 Society of Chemical Industry     

UHMWPE纤维的熔融行为和结晶结构的研究

用DSC法研究了超高相对分子质量聚乙烯(UHMWPE)纤维的熔融行为。随着拉伸倍数提高,纤维经松弛状态下热处理后,其熔融峰数目由1个变为2个;而经部分张力和张力状态下热处理后,其熔融峰数目均由1个变为3个。熔融峰出现的位置可分为4个区:131-138℃,141-143℃,150-152℃,155- 157℃。松弛与张力状态下热处理纤维的主熔融峰不同,前者主要是正交晶系的熔融,后者则分别对应于正交晶相向六方晶相的转变和六方晶相的熔融。经热处理的UHMWPE纤维的DSC图谱表明,代表正交晶相向六方晶相转化的熔融峰面积均有所增大,同时纤维的拉伸强度均有提高,提高幅度达31.1%。     

Effect of self‐nucleation on crystallization and melting behavior of polypropylene and its copolymers

The effect of self‐nucleation on the crystallization and melting behavior of isotactic polypropylene (i‐PP) and low ethylene content propylene–ethylene copolymers were investigated. Isothermal crystallization kinetics were studied using the Avrami equation and Lauritzen‐Hoffman nucleation theory. It was found that self‐nucleation can enhance the crystallization. The surface free energy ς_e decreased for the self‐nucleated sample. The melting behavior was affected by the preselected temperature, T_s, at which the polymer was partially melted. © 1999 John Wiley & Sons, Inc. J Appl Polym Sci 72: 1559–1564, 1999     

Ultradrawing properties of ultrahigh‐ molecular‐weight polyethylene/carbon nanotube fibers prepared at various formation temperatures

The influence of formation temperature on the ultradrawing properties of ultrahigh‐molecular‐weight polyethylene/carbon nanotube (UHMWPE/CNT) fiber specimens is investigated. Gel solutions of UHMWPE/CNT with various CNT contents were gel‐spun at the optimum concentration and temperature but were cooled at varying formation temperatures in order to improve the ultradrawing and tensile properties of the UHMWPE/CNT composite fibers. The achievable draw ratio (D_ra) values of UHMWPE/CNT as‐prepared fibers reach a maximum when they are prepared with the optimum CNT content and formation temperature. The D_ra value of UHMWPE/CNT as‐prepared fibers produced using the optimum CNT content and formation temperature is about 33% higher than that of UHMWPE as‐prepared fibers produced using the optimum concentration and formation temperature. The percentage crystallinity (W_c) and melting temperature (T_m) of UHMWPE/CNT as‐prepared fiber specimens increase significantly as the formation temperature increases. In contrast, W_c increases but T_m decreases significantly as the CNT content increases. Dynamic mechanical analysis of UHMWPE and UHMWPE/CNT fiber specimens exhibits particularly high α‐transition and low β‐transition, wherein the peak temperatures of α‐transition and β‐transition increase dramatically as the formation temperature increases and/or CNT content decreases. In order to understand these interesting drawing, thermal and dynamic mechanical properties of the UHMWPE and UHMWPE/CNT as‐prepared fiber specimens, birefringence, morphological and tensile studies of as‐prepared and drawn fibers were carried out. Possible mechanisms accounting for these interesting properties are proposed. Copyright © 2010 Society of Chemical Industry     

Synthesis and characterization studies of homopolymers of N-vinylpyrrolidone,vinyl acetate,and their copolymers

Homopolymers of N-vinylpyrrolidone (VP) and vinyl acetate (VAc) were synthesized by a free-radical solution polymerization technique. Copolymers of VP and VAc in various monomer feed ratios were also synthesized by the same procedure. They were characterized by elemental analysis, FTIR, PNMR, TGA, swelling, and viscosity measurements. The reactivity ratios of the monomers were computed by both Fineman–Ross and Kelen–Tudos methods using data from both PNMR and elemental analysis studies. The activation energy values for various stages of decomposition were calculated from TGA analysis using Broido's method. The viscosity measurements were carried out at four different temperatures: 30, 35, 40, and 45°C. The activation parameters of the viscous flow, voluminosity (V_E), and shape factor (ν) were also computed for all systems. © 1998 John Wiley & Sons, Inc. J Appl Polym Sci 68:91–102, 1998     

Comparison of thermomechanical properties of statistical, gradient and block copolymers of isobornyl acrylate and n-butyl acrylate with various acrylate homopolymers

Well-defined statistical, gradient and block copolymers consisting of isobornyl acrylate (IBA) and n-butyl acrylate (nBA) were synthesized via atom transfer radical polymerization (ATRP). To investigate structure-property correlation, copolymers were prepared with systematically varied molecular weights and compositions. Thermomechanical properties of synthesized materials were analyzed via differential scanning calorimetry (DSC), dynamic mechanical analyses (DMA) and small-angle X-ray scattering (SAXS). Glass transition temperature (T_g) of the resulting statistical poly(isobornyl acrylate-co-n-butyl acrylate) (P(IBA-co-nBA)) copolymers was tuned by changing the monomer feed. This way, it was possible to generate materials which can mimic thermal behavior of several homopolymers, such as poly(t-butyl acrylate) (PtBA), poly(methyl acrylate) (PMA), poly(ethyl acrylate) (PEA) and poly(n-propyl acrylate) (PPA). Although statistical copolymers had the same thermal properties as their homopolymer equivalents, DMA measurements revealed that they are much softer materials. While statistical copolymers showed a single T_g, block copolymers showed two T_gs and DSC thermogram for the gradient copolymer indicated a single, but very broad, glass transition. The mechanical properties of block and gradient copolymers were compared to the statistical copolymers with the same IBA/nBA composition.     

Two equilibrium melting temperatures and physical meaning of DSC melting peaks in poly(ethylene terephthalate)

For poly(ethylene terephthalate), two equilibrium melting temperatures, 262 °C and 276 °C, were found with DSC. They should be assigned to two forms of crystals with the infinite crystal length, respectively. This finding made it possible every crystal form to derive the end surface free energy per unit area of crystals and the transition enthalpy of the ordered parts in the amorphous regions and using these thermodynamic quantities to convert DSC melting curves into the crystal length distribution. Through the derivation of them, the participation of the crystallization temperature on cooling in the thermal analysis of DSC melting curves was revealed thermodynamically.     

Influence of alternating sequential fraction on the melting and glass transition temperatures of ethylene-tetrafluoroethylene copolymer

The melting (T_m) and glass transition (T_g) temperatures of a series of ethylene (E)-tetrafluoroethylene (TFE) copolymer (ETFE) have been found to show unique dependence on the TFE content with the minimal and maximal points. These behaviors have been interpreted successfully on the basis of the degree of alternation of E and TFE monomeric units along the skeletal chain. The melting point of a perfectly alternating copolymer is estimated to be 295 °C on the basis of the dependence of T_m using a modified Flory’s equation. The corresponding T_g was estimated as 145 °C by applying a modified Gibbs-Damnation’s equation.     

A lattice‐fluid,group‐contribution treatment of the glass transition of homopolymers,copolymers, and polymer solutions

The glass transition temperature of polymers and polymer solutions was approached through a combination of the group‐contribution, lattice‐fluid equation of state and the Gibbs–DiMarzio criterion. The model assumes zero entropy at the glass transition temperature and treats molecules as semiflexible chains. This stiffness is associated with a flex energy obtained from the glass transition temperature at atmospheric pressure. Whereas the application of the model is straightforward for homopolymers and polymer solutions, a new formalism using the dyad concept was developed for copolymers. It takes into account the copolymer composition as well as the sequencing of the monomers. The results obtained are consistent with experimental data. For polymer solutions, the model predictions are semiquantitative depending on the system. The interaction parameter required for binary systems was found to have little effect on the glass transition temperature predictions. © 2003 Wiley Periodicals, Inc. J Appl Polym Sci 89: 697–705, 2003     

Synthesis and characterization of side-chain liquid crystalline homopolymers and block copolymers containing biphenyl-4-ylthiophene and biphenyl-4-ylfluorene pendants

A series of new liquid crystalline homopolymers (P1 and P2) and block copolymers (P3 and P4) composed of methacrylates containing pendant biphenyl-4-ylthiophene (M1) and biphenyl-4-ylfluorene (M2) units were synthesized by atom transfer radical polymerization (ATRP). The number-average molecular weights (M_n) of the homopolymer (P2) and diblock copolymers (P3 and P4) were in the range of 5153-8713 g mol⁻¹ with polydispersity indices (PDIs) between 1.17 and 1.25. The thermal, mesogenic, and photoluminescence (PL) properties of all polymers were investigated. Except for the absence of mesogenic properties in block copolymer P4, polymers P1 and P3 possessed the smectic A phase and polymer P2 exhibited the nematic phase. Moreover, the mesomorphism and the layer d-spacing values of the smectic A phase in polymers P1 and P3 were confirmed and characterized by X-ray diffraction (XRD) patterns.     

Solution and quasi‐bulk copolymerizations of styrene and methyl methacrylate in the presence of polybutadiene: Mathematical model

A mathematical model was developed for simulating the batch copolymerization of styrene (St) and methyl methacrylate (MMA) in the presence of polybutadiene (PB). It was adjusted to the measurements of three reactions carried out at 65°C, with initial comonomers ratio at the azeotropic condition, THF as solvent, and benzoyl peroxide as initiator. The measurements included: (a) conversions and grafting efficiencies by gravimetry; (b) molecular weight distributions (MWDs) by size exclusion chromatography; and (c) global mass fractions of St in the co‐ and terpolymer, by UV‐Vis spectroscopy. The model predicts the MWDs of the three polymeric components of MBS: free St‐MMA copolymer, St‐MMA‐g‐PB graft terpolymer (GT), and residual PB. In addition, it predicts the bivariate chain length distributions of the different GT topologies, with each topology characterized by the number of branches per molecule. © 2010 Wiley Periodicals, Inc. J Appl Polym Sci, 2010     

Bulk polymer/solvent interactions for polyethylene and EVA copolymers,below their melting temperatures

In this work, the Flory–Huggins parameters corresponding to the amorphous phase of a polyethylene (PE) and two ethylene–vinyl acetate (EVA) copolymers (with 18 and 33 % vinyl acetate content, respectively) samples, with different solvents have been determined below the melting temperature of the polymers, in order to quantify the bulk interactions of these polymer/solvent systems. The employed solvents were a dispersion solvent (cyclohexane), a polar solvent (vinyl acetate) and an association solvent (methanol). Initially, the inverse gas chromatography measurements allowed obtaining the retention volumes, activity coefficients and overall Flory–Huggins parameters of every polymer/solvent system. According to these parameters, in all cases, the more compatible solvent was cyclohexane, so it was selected as the probe to calculate the percentages of crystallinity at room temperature, whose results were in agreement the literature data (35 % for PE, 29 % for EVA18, and 12 % for EVA33). The percentage of crystallinity allowed determining the amorphous Flory–Huggins parameters which are the ones which take into account just the bulk interactions in a polymer/solvent mixture. The Flory–Huggins parameter results show that, to accurately study the vapor–liquid equilibrium between a polymer and a solvent (bulk interactions), when the range of studied temperatures is below the melting point of the polymer, it is crucial to calculate the amorphous contribution (χ _amorphous) on the overall Flory–Huggins parameter. In the case of this study, the lower the vinyl acetate content (higher crystallinity), the higher the difference between the overall and amorphous Flory–Huggins parameters is. Analyzing the interactions between the three polymeric materials and the solvents it can be noticed that, for the most compatible solvent (cyclohexane), χ _amorphous represents the less contribution, or the highest correction, to the overall Flory–Huggins parameter (around 50 % for PE and EVA18, and 79 % for EVA33, the less crystalline polymer).