Homopolymers linear

A monomer is a reactive molecule that has at least one functional group (e.g. -OH, -COOH, -NH2, -C=C-). Monomers may add to themselves as in the case of ethylene or may react with other monomers having different functionalities. A monomer initiated or catalyzed with a specific catalyst polymerizes and forms a macromolecule—a polymer. For example, ethylene polymerized in presence of a coordination catalyst produces a linear homopolymer (linear polyethylene) ... 

The CCD curve shown in Fig. 15 contains all the information on composition distribution and it is a common practice to compare the CCD curves of the different resins to be evaluated In addition to the CCD curve, it is convenient to work with some easy-to-use average parameters. In the case of multiple peaks (like those shown in Fig. 15), integration of the peaks is most appropriate. In bimodal LLDPE, the most important parameters to measure are the homopolymer (linear) and soluble fraction percentages. Calculation of moments similar to... 

Joining similar CRU Homopolymers (linear, branched, dendritic, cross-linked, etc.)... 

A polymer, by conventional definition, is a macromolecule made up of multiple equivalents of one or more monomers linked together by covalent bonds (e.g., carbon-carbon, amide, ester, or ether bonds) [1]. These conventional polymers come in many configurations for example, linear homopolymers, linear copolymers, block copolymers, cross-linked polymers, dendritic polymers. 

Ethyne Acetal, Homopolymer (POM Homopolymer) Linear Low Density Polyethylene (LLDPE) Low Density Polyethylene (LDPE) Nylon 12 (PA 12) Nylon 46 (PA 46) Nylon 6 (PA 6) Nylon 610 (PA 610) Nylon 66 (PA 66) Polyamide, Nylon Polycaprolactones Polyethylene Polyethylene Terephthalate (PET) Polyethylene, HDPE Polypropylene Linear Low Density Polyethylene (LLDPE) 9... 

Acetal, Homopolymer (POM Homopolymer) Linear Low Density Polyethylene (LLDPE) Low Density Polyethylene (LDPE)... 

Anionic polymerization methods have been used to synthesize a wide variety of macromolecules including linear [1] and cyclic [2] homopolymers, linear copolymers [1], and functional polymers such as macromonomers [3]. These macromolecules are well defined with predetermined molar masses, sharp molar mass distributions, and low compositional heterogeneity. They serve as ideal compounds to establish the relation between the structure, the properties, and theory. 

Homopolymer. Acetal homopolymers are prepared from formaldehyde and consist of high-molecular-weight linear polymers of formaldehyde. 

Just as it is not necessary for polymer chains to be linear, it is also not necessary for all repeat units to be the same. We have already mentioned molecules like proteins where a wide variety of different repeat units are present. Among synthetic polymers, those in which a single kind of repeat unit are involved are called homopolymers, and those containing more than one kind of repeat unit are copolymers. Note that these definitions are based on the repeat unit, not the monomer. An ordinary polyester is not a copolymer, even though two different monomers, acids and alcohols, are its monomers. By contrast, copolymers result when different monomers bond together in the same way to produce a chain in which each kind of monomer retains its respective substituents in the polymer molecule. The unmodified term copolymer is generally used to designate the case where two different repeat units are involved. Where three kinds of repeat units are present, the system is called a terpolymer where there are more than three, the system is called a multicomponent copolymer. The copolymers we discuss in this book will be primarily two-component molecules. We shall discuss copolymers in Chap. 7, so the present remarks are simply for purposes of orientation. 

The chemical iadustry manufactures a large variety of semicrystalline ethylene copolymers containing small amounts of a-olefins. These copolymers are produced ia catalytic polymerisation reactions and have densities lower than those of ethylene homopolymers known as high density polyethylene (HDPE). Ethylene copolymers produced ia catalytic polymerisation reactions are usually described as linear ethylene polymers, to distiaguish them from ethylene polymers containing long branches which are produced ia radical polymerisation reactions at high pressures (see Olefin POLYMERS, LOWDENSITY polyethylene). 

Similarly, the random introduction by copolymerization of stericaHy incompatible repeating unit B into chains of crystalline A reduces the crystalline melting point and degree of crystallinity. If is reduced to T, crystals cannot form. Isotactic polypropylene and linear polyethylene homopolymers are each highly crystalline plastics. However, a random 65% ethylene—35% propylene copolymer of the two, poly(ethylene- (9-prop5lene) is a completely amorphous ethylene—propylene mbber (EPR). On the other hand, block copolymers of the two, poly(ethylene- -prop5iene) of the same overall composition, are highly crystalline. X-ray studies of these materials reveal both the polyethylene lattice and the isotactic polypropylene lattice, as the different blocks crystallize in thek own lattices. 

The distinctions between these homopolymers arise from the different ways in which the monomer units are hooked together in polyacetal chains. Starch (qv), plant nutrient material, is composed of two polysaccharides a-amylose and amylopectin. cx-Amylose is linear because of exclusive a (1 — 4) linkages, whereas amylopectin is branched because of the presence of a (1 — 6) as well as a (1 — 4) links. The terms linear and branched refer only to primary stmcture. 

Hexachlorocyclotriphosphazene (cycHc trimer) is a respiratory irritant. Nausea has also been noted on exposure (10). Intravenous and intraperitoneal toxicity measurements were made on mice. The highest nonlethal dose (LDq) was measured as 20 mg/kg (11). Linear chloropolymer is also beUeved to be toxic (10). Upon organic substitution, the high molecular weight linear polymers have been shown to be inert. Rat implants of eight different polyphosphazene homopolymers indicated low levels of tissue toxicity (12). EZ has been found to be reasonably compatible with blood (13), and has lower hpid absorption than fiuorosihcone. 

Epichlorohydrin Elastomers without AGE. ECH homopolymer, polyepichlorohydrin [24969-06-0] (1), and ECH—EO copolymer, poly(epichlorohydrin- (9-ethylene oxide) [24969-10-6] (2), are linear and amorphous. Because it is unsymmetrical, ECH monomer can polymerize in the head-to-head, tail-to-tail, or head-to-tail fashion. The commercial polymer is 97—99% head-to-tail, and has been shown to be stereorandom and atactic (15—17). Only low degrees of crystallinity are present in commercial ECH homopolymers the amorphous product is preferred. 

The homopolymers of p-hydroxybenzoic acid have such a high value for the that they are somewhat intractable. Useful materials may, however, be made by copolymerising with a view to introducing some molecular flexibility or reducing chain packing or introducing some non-linear links. Commercially important liquid crystal polyesters are discussed in Chapter 25. 

The glass transition temperature of a random copolymer usually falls between those of the corresponding homopolymers since the copolymers will tend to have intermediate chain stiffness and interchain attraction. Where these are the only important factors to be considered a linear relationship between Tg and copolymer composition is both reasonable to postulate and experimentally verifiable. One form of this relationship is given by the equation... 

Whereas the glass transition of a copolymer is usually intermediate between those of the corresponding homopolymers this is not commonly the case with the melting points. Figure 4.12 shows the effect of copolymerising hexamethylenesebacamide with hexamethyleneterephthalamide. Only when the monomer units are isomorphous, so that the molecules can take up the same structure, is there a linear relationship between melting point and composition (as with hexamethyleneadipamide and hexamethyleneterephthalamide). 

At the end of the 1970s considerable interest developed in what became known as linear low density polyethylenes (LLDPE) which are intermediate in properties and structure to the high pressure and low pressure materials. While strictly speaking these are copolymers it is most convenient to consider them alongside the homopolymers. The LLDPE materials were rapidly accepted by industry particularly in the manufacture of film. The very low density polyethylenes (VLDPE) introduced by Union Carbide in 1985 were closely related. 

The copolymers are prepared using a mixture of dimethyl terephthalate and dimethyl naphthalate. Published data indicates a reasonably linear relationship between and copolymer composition on the lines discussed in Section 4.2, e.g. Tg for a 50 50 copolymer is about 100°C which is about mid-way between Tg figures for the two homopolymers. In line with most other copolymers there is no such linearity in the crystalline melting point (T, ). As comonomer levels are introduced drops from the values for both homopolymers and indeed crystallisation only readily occurs where one of the components is dominant, i.e. 80%. Thus commercial copolymers are usually classified into two types ... 

The main results of this miero-mechanical model in the quasi-static regime have been compared with experimental results obtained by placing polystyrene (PS)-polyvinyl pyridine (PVP) diblock copolymers with a short PVP block between PS and PVP homopolymers. The fracture toughness was found to increase linearly with E from that of the bare PS/PVP interface, while the slope of the line increased with the degree of polymerization of the block being pulled out. If the data for the different copolymers were plotted as AG vs. (where... 

A. N. Semenov, J. F. Joanny. Kinetics of adsorption of linear homopolymers onto flat surfaces Rouse dynamics. J Physique II 5 859, 1995. 

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