SYNTHETIC POLYMERIC AMPHOLYTES IN SOLUTION

Abstract

Polyampholytes are classified as polyelectrolytes whose macromolecules contain functional groups of acidic and basic character [1, 2]. They possess unique physicochemical properties due to the contamination of oppositely charged units in the polymer chain. The interest in studying polyampholytes arises because they include such important natural polymers as proteins and nucleic acids [3]. Biopolymers possess specific structures, functions, and properties which are fully revealed only in living organisms [4]. Nevertheless, some properties of natural polymers can be simulated by using synthetic amphoteric macromolecules.     

Molecular Imprinting Fibrous Membranes of Poly（ acrylonitrile-co-acrylic acid） Prepared by Electrospinning

Introduction Overthepastfewdecades,molecularimprinting hasbeendescribedasatechnologyforpreparing“mo leculardoors”whichcanbematchedto“template keys”.Ithasbeenfoundtobeasimpleandeffective approachtointroducespecificrecognitionsitesintosyn theticpolymers…     

Synthesis and Characterization of One-dimensional and Two-Dimensional Porphyrin Polymers (Ⅰ)

Porphyrin polymers are of interest in relation to conductive materials[1, 2], catalysts for photosynthetic charge separation[3], or the fundamental features in biological systems[4]. There have been many versatile studies about them[5.6]. The one-dimensional "Shish Kebab"porphyrin polymers synthesized with a new method different from those reported and Schiff-base porphyrin polymers with two-dimensional nano-structure have provided a new field of study. The present paper covers highly ordered…     

Synthesis of Poly（aryl ether ketone） Copolymers Containing Adamantyl-substituted Naphthalene Rings

1 Introduction High performance polymers have received con-siderable attention over the past decade owing to their increased demands as replacements for metals or     

Hydrothermal Synthesis,Crystal Structure and Thermal Properties of a Novel Samarium Complex with 1D Nano-chain Structure

1 Introduction The design and construction of metal-organic polymers has been a field of rapid growth in materials chemistry because of their intriguing topologies and potential applications as functional materials[1―6]. In     

Pyrolysis of flame retardants and fire protected polymers

The simultaneously working combination of thermal analysis and mass spectrometry (TA/MS) is a very useful method for studying the degradation process of polymeric materials during thermal treatment [1–7]. Beside the thermal effects, as recorded from thermogravimetry (TG) or differential thermal analysis (DTA) the evolved degradation products can be determined and identified by the on - line coupled mass spectrometer. Additional their temperature depending abundance can be registrated. Combustion of polymers in horizontal (BIS) or vertical (VCI) furnaces and subsequent off line high resolution GC/MS analysis of pyrolysis products is suitable for the simulation of burning processes     

Effects of Heat Treatment on the Crystallization Behavior of Poly(3-alkylthiophenes)

IntroductionPoly( 3- alkylthiophenes) ( P3ATs) ,as a newkind of soluble,fusible and processable conductivepolymers,have attracted a great interest and muchattention ofchemistsand physicists[1,2 ] . Ithas beenwidely accepted that P3ATs can form similarlayered structures with alkyl side chains beingoriented in the lateral a- axis direction[3— 6] .Moreover,when the number of the carbon atoms inthe alkyl side chains is more than1 0 ,some orderlyarrangements of the side chains will occur between…     

Orientational Measurements in Polymers Using Vibrational Spectroscopy

The mechanical properties of polymers are strongly influenced not only by the structure of the material but by the magnitude of the molecular orientation. Thus a great deal of interest exists in information about the molecular orientation in samples introduced by drawing or other forming processes. Several techniques of evaluation of this orientation exist such as birefringence, x-ray diffraction, sonic modulus, and fluorescence measurements [l, 2]. Vibrational analysis of oriented polymers provides a method of determining independently the molecular orientation both in the crystalline and amorphous phases of polymers. By using vibrational techniques, a number of macromolecules have been studied in the solid state for a variety of different processes. It is the purpose of this review to summarize the recent theoretical and experimental results which have occurred since the review of Zbinden [3]. Infrared and Raman measurements will be reported since they are complementary to each other in their applications and results.     

Influence of γ-ray Irradiation on the PTC Effect of EPDM/Carbon Black Composite

Introduction The positive temperature coefficient(PTC) effect is characterized by an increase of resistivity with an elevated temperature.The PTC effect of carbon black(CB) filled polymers is useful for self-regulation heaters,over-current protectors,sensors,etc.Much work has been done on the PTC effect of the carbon black filled crystalline polymer composite[1-4],whereas carbon black filled amorphous polymers have not drawn researchers much attention because the PTC effect in these composites is small or cannot be detected[5-7].In this work,the influence of γ-ray irradiation on the PTC effect of CB filled amorphous ethylene-propylene-diene terpolymer(EPDM) composites was studied.     

Internal motion in some aromatic polyesters and linear aromatic chains

Low-temperature internal motions of the following polyesters have been investigated by broad line nuclear magnetic resonance: poly(methylene terephthalates) (2–6 methylene groups), poly[1,4-(dimethylene)cyclohexylene terephthalate], poly(diethyleneglycol terephthalate), poly(1,2-propylene terephthalate), poly(1,4-phenylene terephthalate), poly(2,2,3,3,4,4-hexafluoropentamethylene terephthalate), poly[1,4-phenylenebis(dimethyl) siloxane], and poly(2,6-dimethylphenylene oxide). No complex line structure was found for any of the samples. Molecular motions in the polyesters appear to be restricted by polar forces arising from the ester groups. Above—196°C. the line width decreases smoothly with increasing temperatures for all polymers except poly[1,4-(dimethylene)cyclohexylene terephthalate] and poly[1,4-phenylenebis(dimethyl)siloxane]. These two show a definite transition in line width at ?20°C. and +12°C., respectively, caused by the onset of considerable internal motion. At ?196°C. the lattices are rigid except for polymers containing methyl groups: poly(1,2-propylene terephthalate), poly[1,4-phenylenebis(dimethyl) siloxane], and poly(2,6-dimethylphenylene oxide). Internal motion that can be ascribed to be a reorientation of the methyl groups is present at ?196°C. for these three polymers, as is demonstrated by comparison of experimental second moments and those calculated on the basis of various models.     

Extended coordination frameworks incorporating heterobimetallic squares

The molecular structure of aluminium and iron(III) complexes with 3-phenyl and 3-(4-pyridyl) (HL) substituted acetylacetonate ligands is appreciably distorted. For AlL3 and FeL3 this shows that the orientation of the side pyridyl-N donor atoms lone pairs is about 90 and 135 degrees which favours the assembly of heterobimetallic square patterns in Al(Fe)L3 complexes with metal ions. This was employed for the modular construction of semi-regular heterobimetallic networks, in which the pyridyldiketonate ligands bridge pairs of Fe(Al)/Cd(Co) metal ions and support the structure of 1D and 2D coordination polymers. The unprecedented 2D structure of [Cd[AlL3](CH3OH)[NO3]2].2CHCl3 and Cd[AlL3](CH3OH)Br2].2CHCl3 . 2CH3OH is based upon plane tiling by a set of heterobimetallic squares and octagons, while [Cd[FeL3]2(NO3)2].2H2O and [Co[AlL3]2Cl2].4CHCl3 . 2CH3OH are 1D polymers and exist as chains of heterobimetallic squares sharing opposite vertices.     

An Alternative Way towards Preparation of Hydrophobically Associating Polyacrylamide:Chemical Post-Modification

Hydrophobically associating polyacrylamides (HAPAMs) are derivatives from polyacrylamides by incorporating a small amount of hydrophobic moieties along the water-soluble mainchain. They are now becoming a class of promising candidates as thickeners or rheology modifiers in the formulations where rheology is necessary to be regulated, such as tertiary oil recovery, drilling fluids, hydraulic fracturing and coatings. Due to association of hydrophobes in nano-domains, their aqueous solutions exhibit very interesting rheological properties and better stability against salts than the unmodified precursor, polyacrylamide.Generally, there are two synthetic routes to introduce hydrophobic portion onto water-soluble polymer chains; i.e., direct copolymerization of hydrophobic and hydrophilic monomers, and post-polymerization functionalization[1]. In the case of HAPAM polymers, a commonly accepted method is micellar copolymerization in which an appropriate surfactant is employed to solubilize both monomers. However, it is widely reported[2] that the obtained polymers via micellar polymerization are characterized by: (i) blocky distribution of the hydrophobes; (ii) compositional inhomogeneity and (iii) strong dependence of solution properties on the block length.In this work, the alternative process, i.e., chemical post-modification, is employed to synthesize HAPAM polymers by direct N-alkylation of parent polyacrylamide (Figure 1) in dimethyl sulfoxide[3,4].PAM HAPAMFig. 1 Schematic route to prepare HAPAM by direct N-alkylation of PAMIt is found that the final incorporation of hydrophobic groups is in good agreement with the feed ratio[4], in contrast with that from micellar copolymerization which always brings about composition drift. Furthermore, unique rheological responses to shear rate, salt, temperature are also evidenced[5].     

Shear-induced Stabilization of the Nematic Phase in a Side Group-containing Poly (aryl ether ketone) Copol ymer

IntroductionPolarized optical microscopes (POM) are commonly used to identify liquid crystalline tex-tures. However, it is often found problematic to employ this technique in investigating themesophase transition of polymeric materials due to their higher viscosities. Rheological mea-surements at this juncture could provide us with valuable information about the mesophase- transition of liquid crystalline polymers[1]. Accordingly, there have been some rheological in-vestigations reported on …     

Syntheses and Investigation of Some New Polyarylates and Copolyarylates. Part I

By the interfacial condensation of acid chlorides I, II, and III, respectively, with bifunctional phenols (IV-X), soluble or mold-able thermostable polyarylates were obtained. Similarly, copolyarylates were prepared from a mixture of the acid chlorides I + II or I + III. With bisphenol-A (VIII), soluble polymers are usually obtained. Methylene dichloride and/or carbon tetra-chloride-water systems were the best media for interfacial condensations, and the polymers formed showed the highest reduced viscosity values.

Polyester films are useful in many industrial applications because of their broad range of mechanical, optical, and electrical properties. The aromatic polyesters‐polyarylates-dominate the field of industrial polyester films [1].

Polyarylates prepared from dihydric phenols and purely aromatic dicarboxylic acid chlorides are highly heat resistant materials [2], but they are insoluble and nonmoldable [3]. However, by the introduction of ether linkages in the aromatic dicarboxylic acid moiety, soluble and/or moldable polyamides were obtained [4].     

A Modified Synthesis of 9-(1,2-Dichlorovinyl)carbazole by Using Crown Ethers and Cryptands in a Non-aqueous System

The 9-[(E)-1,2-dichloroviny1]carbazole is a starting material for synthesis of 9-ethynyl-carbazole [1], which in term is monomer for preparation of photoconductive polymers [2]. Dichlorovinylation of carbazole in a solid-liquid two phase system in the presence of crown and cryptand catalysts has been studied. Application of the Phase Transfer Catalysis in the nonaqueous system increases yield of 9-[(E)-1,2-dichloroviny1]carbazole in comparison to the methods based on liquid-liquid system with benzyltriethylammonium chloride (TEBA) or dimethylsulfoxide (DMSO) as catalysts.     

Two Novel Copper(Ⅱ) Complexes with A Novel Ligand 2,4-Di(2-aminopyridine)-6-methylpyrimidine

Introduction The design and syntheses of multidentate N-donor ligands have become the focus of much inter-est in the chemical field[1-4]because these ligands can form multinuclear metalxompounds, coordina-tion polymers and supramolecular compounds,which play a very important role in the bilolgicalsystems, magnetic materials,electric materials,optical materials and otherfields[5-8].     

PERFORMANCE AND MECHANISMS OF HINDERED AMINE LIGHT STABILIZERS IN POLYMER PHOTOSTABILIZATION

Abstract

Hindered amine light stabilizers (HALS) have probably been the most studied compounds in the field of polymer stabilization overthe past 15 years [1–16]. Their excellent performance in polyolefins [1–8], poly(vinyl chloride) [9], polystyrene [10], rubbers [11], polyamides [12], and other polymers such as acrylic resins 113–161 has made them an attractive item for research. There have been many advances regarding the understanding of the nature of the stabilization mechanism of these compounds, and there is still a great amount of controversy particularly with regard to the relative importance of some reactive intermediates [1–16]. This continuing research has led to the development of some novel compounds which are more efficient and have better compatibility with the polymer [1–16]. This article reviews the current understanding of the mechanism of action of HALS, its relationship with their performance in polymers, and their interaction with other additives used in a given stabilization system. The excellent performance of HALS in polyolefins has given rise to a great number of publications on their action in these polymers, and therefore most of the discussion will be related to this.     

Novel Trends in Ladder Polyheteroarylenes

Development of several fields of modern engineering has generated a need for the preparation of polymeric materials with working temperatures as high as 300°C. The solution of this problem is largely connected with preparation of new thermally stable polymers. As a consequence, beginning in the middle of the fifties, numerous investigations were carried out in order to obtain new thermally stable macromolecular compounds [1]. These investigations resulted in a considerable number of organo-element [1] and aromatic carbo-chain polymers [1] with a complex of valuable properties; but the chemistry of aromatic polymers containing various heterocycles in the main chains of macromolecules, so-called polyheteroarylenes, has received the most development [1].     

Poly (dodecacarborane-siloxanes)

The need for elastomeric polymers which will maintain their elastic properties at high temperatures has led to a wide interest in inorganic-based polymers [l]. The development of carborane-siloxane polymers in the early 1960s was a breakthrough in the search for a high-temperature elastomer. Incorporation of a carborane moiety into the siloxane backbone significantly enhanced the overall thermal stability [2].