Grafting of Vinyl Monomers onto Silk Fibers

Abstract

Graft copolymerization onto textile fibers is a challenging field of research with unlimited future prospects [1–6]. This is attractive to chemists as a means of chemical modification of natural macromolecules since, in general, degradation could be minimized. Thus it is hoped to retain the desirable properties of the natural material and give it additional properties through the added polymer. Means of forming copolymers with natural macromolecules are now well understood because the techniques of polymer chemists are usually applicable. A vast number of combinations of composition and conformation is possible for each copolymer, and the properties of each copolymer may vary with the mode of formation employed.     

GRAFT COPOLYMERIZATION OF CELLULOSE,CELLULOSE DERIVATIVES,AND LIGNOCELLULOSE

Abstract

The growth of polymer science has led to the development of new materials in direct competition with natural materials, many of which have been in use since earliest times. This has caused researchers to look more critically at both natural and synthetic macromolecules in order to learn more about their underlying structures and their relation to the properties exhibited by the macromolecules. In this regard, chemical modifications have been devised to impart certain desirable properties of both natural and synthetic macromolecules, and their applications have become an integral part of such chemical modifications. Various chemical modifications (e.g., change of functionality, oxidative degradation, inter- and intramolecular gelation, graft copolymerization), have been practiced to add improved properties to the base polymers. However, among all these methods, modification of polymers via graft copolymerization has been the subject of much interest and has made paramount contribution toward improved industrial and biomedical applications.     

Ultracentrifuge as a Versatile Tool to Study Preferential Interaction of Polymers in Mixed Solvents

Abstract

Over the past five decades the analytical ultracentrifuge has been a versatile tool in the study of macromolecules and colloidal particles. Several textbooks [1–4] and review articles [5–10] deal with experimental techniques and theories for complete characterization of macromolecular species. However, the first published articles on the analytical ultracentrifuge dealt with the analysis of particle size distributions in suspensions of inorganic colloids. The emphasis has now shifted to organic polymers following the discovery that a large number of such polymers exist in nature. Before the development of the ultracentrifuge, the existence of such giant molecules was not recognized; the molecular kinetic units of proteins and of high organic polymers in solution were simply thought of as clusters of much smaller molecules, forming particles of undefined mass. Beginning with the elegant investigations of Svedberg [11, 12] on ultracentrifugation, such substances were revealed to be macromolecules, large because they contain a huge number of atoms connected together by primary chemical bonds [13]. Following a long and fruitful series of investigations in the early twenties and thirties, Svedberg wrote in one of his articles [12], “the proteins are built up of particles possessing the hallmark of individuality and therefore are in reality giant molecules. We have reason to believe that the particles in the protein solutions and the protein crystals are built up according to a plan which makes every atom in them indispensable for the completion of the structure.” Almost at the same time, it was Staudinger [14] who clearly demonstrated that substances such as polystyrene and natural rubber exist in solution without change in molecular weight regardless of the solvent employed .     

GRAFT COPOLYMERIZATION OF VINYL MONOMERS ONTO JUTE FIBERS

Abstract

Among the various types of copolymerization, graft copolym-erization has attracted considerable attention among applied polymer chemists. Graft copolymerization is a process of copolymerization of one kind of monomer in its polymeric state with another polymer which may be either synthetic or natural. So a graft copolymer is a high polymer whose molecule consists of two or more polymeric parts of different composition, chemically united together. Graft copolymerization onto textile fibers is a challenging field of research with unlimited future prospects [1-10]. This is attractive to chemists as a means of modifying macromolecules since, in general, degradation is minimized. The desirable properties of the polymer are retained, and copolymerization Drovides additional properties throuerh the added polymer.     

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].     

Graft Copolymerization of Vinyl Monomers onto Cellulose and Cellulosic Materials

Abstract

Graft copolymerization is a novel method which has wide application in synthesizing new forms of polymeric materials and also in modifying the properties of natural polymers [1,2]. Much research has been done on grafting polymeric molecules on to cellulose to produce materials of new properties intermediate between those of cellulose and those of synthetics. A variety of property changes can be imparted to cellulose through grafting without destroying the crystallinity or crystallization potential of the substrate or reducing its melting point. Some of the most dramatic changes in properties which have been brought about by grafting to cellulose are viscoelasticity, stereoregularity, hygroscopicity, water repellency, improved adhesion to a variety of substances, settability, soil resistance, bacteriocidal properties, and thermal stability.     

Grafting of Vinyl Monomers onto Nylon

Polymer chemists have been successful in applying polymerization techniques to develop copolymers of natural and synthetic macromolecules [l]. The literature abounds with examples of the successful formation of copolymers from natural and synthetic macromolecules [2–5]. Copolymerization is attractive to chemists as a means of modifying macromolecules since, in general, degradation can be minimized. Despite the heterogeneity and complexity of these copolymers, much has been achieved in their characterization. The desirable properties of the polymer are retained and additional properties are acquired through the added polymer. The desired material may be formed in situ by polymerization of a monomer or monomers, by condensation of reactants, or by the decomposition of a preformed polymer.     

New benzimidazole-2-yl-substituted polybenzimidazoles: Synthesis, properties, and hydrodynamic characteristics

The synthesis of novel benzimidazole-2-yl-substited polybenzimidazoles and initial compounds has been described. The polymers are studied by FTIR spectroscopy, TGA, and TMA. The hydrodynamic properties of macromolecules are investigated by translational diffusion and viscometry in 96% H₂SO₄; the molecular characteristics of the polymers are determined. Positive temperature dependences for intrinsic viscosities of the polymers are obtained. The polymers under study possess high hydrolytic stability with respect to sulfuric acid solutions up to 150°C and high thermal stability in the bulk. The TGA data correlate with the chemical structure of the polymers. The new polybenzimidazoles may be used as materials for the production of medium-temperature proton-conducting membranes.     

An Engineering Approach to Polymer Solution Properties

Abstract

Numerous theories of polymer solution behavior have been advanced. Some make use of the techniques of statistical mechanics [1] and are unfortunately burdened with tedious mathematical manipulations, Recent years have seen the emergence of the socalled scaling laws of de Gennes [2]. These are mainly of theoretical interest and are strictly applicable to polymers with very high molecular weight in good solvents, While these theories are important as steps toward a fundamental understanding of polymer solutions, they are not easy to understand or apply to practical calculations of polymer solution properties.     

Hydrodynamic,optical, and electrooptical properties of macromolecules of third-generation cylindrical dendrimers in chloroform and dichloroacetic acid

Acrylic polymers containing side dendrons of the third generation based on L-aspartic acid have been studied via the methods of molecular hydrodynamics, dynamic and static light-scattering, optics, and electrooptics. There are marked differences in hydrodynamic and optical properties of the macromolecules under study and previously examined polymers with side dendrons of first and second generations. In the range of degrees of polymerization from 10 to 40, these macromolecules possess an extremely low shape asymmetry. Experiments demonstrate the predominant orientation of end side dendrons along the main molecular chain. In chloroform solutions, the orientation of macromolecules in hydrodynamic and electric fields occurs according to the large-scale mechanism. In dichloroacetic acid, the hydrodynamic dimensions of macromolecules decrease, an effect that is accompanied by an increase in the kinetic flexibility of polymer chains.     

Amino Acid and Poly(Ethylene Glycol) Based Self-Organizing Polymeric Systems: Chemo-Enzymatic Synthesis and Characterization

A chemo/regio selective enzymatic methodology has been designed to synthesize amphiphilic copolymers based on amino acid diesters and poly(ethylene glycol) [PEG]. The condensation polymerization was catalyzed by immobilized Candida antarctica lipase B (Novozyme 435) under solvent-less conditions. The synthesized polymers 3a–c were derivatized with long chain acid chlorides by chemical acylation to get the amphiphilic polymers 4a–c. The physical properties of the synthesized amphiphilic polymers viz: aggregation number, critical micelle concentration (CMC), radius of gyration (R_g), hydrodynamic radius (R_h) and particle size distribution were studied by static and dynamic light scattering (SLS and DLS) techniques. The polymers were found to be promising in drug delivery applications.     

DEGRADATION AND STABILIZATION OF POLY(VINYL CHLORIDE)

Abstract

Poly(viny1 chloride) (PVC) has many desirable characteristics that have allowed it to achieve its present status as one of the most important commercial polymers. In spite of its enormous technical and economic importance, PVC still possesses many problems. Its rather low stability to the influence of heat and light results in discoloration, hydrogen chloride loss, and serious corrosion phenomena [1], accompanied by changes in the mechanical properties of the article together with a decrease or an increase in molecular weight as a result of chain sassion or crosslinking of the polymer molecules, respectively [2].     

Solution Properties of Water-Soluble Nonionic Polymers

Abstract

Water-soluble nonionic polymers occupy a special place among synthetic polymeric materials. Most of them possess a number of unique properties allowing various industrial and medicinal applications. Such important industrial branches as coal mining, oil recovery, production of textiles, paper, lacquers, adhesives, cosmetics, and medicinal preparations cannot be conceived without these polymers. For instance, poly(acrylamide) and poly-(oxyethylene) can decrease pressure losses, increase considerably the drilling time, reduce the time of flooding underground spaces, and increase the speed of ship movement and pumping of liquids. Very important is the role of water-soluble nonionic polymers in the textile industry where they have successfully replaced expensive natural materials in the processes of cloth sizing and finishing and are used in the production of new kinds of fabrics possessing high mechanochemical characteristics. The use of these polymers is also important in medicine due to their good compatibility with water, high tendency to complex, and lack of toxicity.     

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.     

Soluble Intermacromolecular Complexes Formed between Carboxymethyl Cellulose and Water-soluble Polymer with Complementary Structure

Homogenous complexation of water-soluble polymers with chemically complementary structures in aqueous media has recently attracted great interest^[1]. It is known that such macromolecules in solution can interact with each other, resulting in excluded volumes and ordered structures through the formation of soluble intermacromolecular complexes^[2]. Therefore, such systems may possess unique properties that are different from those of individual components and there are many potential applications.     

POLYMERS DERIVED FROM HEXAFLUOROACETONE

Abstract

The continuing demand for polymeric materials with a unique combination of properties has brought forth a sizable research effort concerning the use of trifluoromethyl substituents, particularly the 1,1,1,3,3,3-hexafluoroisopropylidene (HFIP) function derived from the incorporation of hexafluoroacetone (HFA) into the monomer. This work had its beginnings approximately 25 years ago when Rogers briefly reported in a patent the preparation of polyimides (PIs) from an hexafluoroisopropylidenebrideged diamine [1,2]. Since then numerous efforts have been made toward the synthesis, characterization, and evaluation of CF₃-containing polymers. Much of this information is found in patents, indicating the importance of these polymers to industry. At the present time, at least 11 known classes of polymers containing pendant or backbone-incorporated bis-trifluoromethyl groups have been reported. These polymers show promise as film formers, gas separation membranes, seals, soluble polymers, coatings, and in other high-temperature applications. Frequently the polymer properties imparted by the inclusion of the HFIP function encompass: increased solubility, flame resistance, glass transition temperature, thermal stability, oxidation resistance, and environmental stability; decreased color, crystallinity, dielectric constant, and water absorption.     

Note: Synthesis And Crystal Structure Of A Binuclear Fumarate Complexof Copper(II) With 1,10-Phenanthroline

As dicarboxylate complexes of transition metal possess potentially useful electronic and magnetic properties, [Mehrotra and Bohra (1983). Metal Carboxylates. Academic Press, London], much interest in their synthesis and structure has been apparent recently [Kaneko and Tsuchida (1981). J. Polymer Sci . , Macromolecular Reviews, 16, 397; Holton, Lappert, Pearce and Yarrow (1983). Chem. Reviews, 83, 135]. A series of metal complexes bridged by dicarboxylates has been synthesized in our laboratory and crystal structures show versatile coordination modes for the carboxyl group [Cheng, Liu, Xu and Xu (1999). J. Coord. Chem., 48 , 495; Nie, Liu, Luo and Xu (2001). J. Coord. Chem., 53, 365]. As a part of this investigation, we have synthesized a binuclear fumarate complex of Cu(II). X-ray analysis shows considerable coordination distortion resulting from close stacking interaction of aromatic phen rings.     

Structural Design and Applications of Stereoregular Fused Thiophenes and Their Oligomers and Polymers

Abstract

Stereoregular fused thiophenes (SFTs: especially thieno[3,2-b]thiophene (TT) and dithieo[3,2-b:2′,3′-d]thiophene (DTT)), as stable conjugated structures deriving from thiophene ring enlargement, possess outstanding properties and special configuration, such as the superior carrier transfer efficiency and a high degree backbone of planarity. In comparison to stand-alone SFTs structures, oligomers and polymers containing different heteroaromatic units have been much widely researched and used in many fields. In decade, several important reviews have summarized the broad field of fused thiophenes including SFTs, and their synthesis and optoelectronic applications. Here, we critically present the structure–performance relationships and application of oligomers and polymers containing SFTs (exhibiting thiophene ring number from 2 to 7) units. First, the basic structures and properties of SFTs are briefly stated. Then, oligomers classified by extra conjugated heterocyclic attachments are carefully discussed, focusing on the structure–performance relationships for their optoelectronic applications including organic photovoltaic cells and organic field-effect transistors. Moreover, such relationships in polymers have been applied in much wider fields such as organic light-emitting diodes, electrochromic devices, thermoelectric devices, and supercapacitors are discussed. Finally, a summary and prospect are given. Through this review, instruction for molecular design and novel ideas for the future development of SFTs-contained are provided.     

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.     

Electrochemically synthesized polymer of the plant substance embelin (2,5-dihydroxy-3-undecyl-1,4-benzoquinone)

Among the possible new materials for microelectronics, quinones have a number of significant advantages. Similarly, polymers with quinone functionality possess biodegradability. Because natural polymers are promising candidates for functional materials for the future, we have initiated studies on the polymers of natural products. In the present study, a natural quinone (a plant substance) extracted from Embelier libes distributed in the Kerala state of India was electrochemically polymerized and its properties were investigated. The redox activity, electrical conductivity, and biodegradability are discussed.