Copolymer synthesis,

Copolvmer Synthesis. Copolymers were prepared with HEMA (Kodak L d oratory and Research Products, Rochester, NT) 2uid AMPS (Lubrlzol Chemical Corp., Wickliffe, OH) at weight ratios of 78/22, 60/40,... 

A series of enantioselective imprinted polymer membranes for amino acid and peptide derivatives were prepared using oligopeptides as functional monomers [42-45]. A tetrahydrofuran solution containing a template molecule, a functional monomer of a peptide derivative attached on polystyrene resin that is commonly used in solid-phase peptide synthesis, copolymer of acrylonitrile and styrene, was poured into a flat laboratory dish and left for 24 h to remove the solvent. 

Polymer Synthesis. Copolymers of alkylacrylamide (R) and acrylamide (AM), which we called RAM, were prepared with a micellar polymerization technique (4). A micellar surfactant solution was used to disperse the hydrophobic alkylacrylamide monomer into an aqueous phase that contained acrylamide. The monomers were polymerized with a standard free-radical initiator (e.g., potassium persulfate) or a redox initiator to yield the desired random copolymer. Varied temperature and initiator concentrations were used to provide polymers of different molecular weights. Polymerizations were taken to essentially complete conversion. Compositions, in terms of hydrophobe level reported in this chapter, were based on amounts charged to the reactor. Further details on the synthesis and structure of these RAM polymers... 

Method of synthesis copolymers are produced by high-temperature/high pressure free radical polymerization similar to the one used In production of LDPE. Carboxyl groups are completely or partially neutralized to form ionomers (mostly Na or Zn). Neutralization extent Increase causes adequate Increase in viscosity of material ... 

Method of synthesis. copolymers are synthesized through anionic polymerization Canto, L B Mantovani, G L ... 

To illustrate the specific operations involved, the scheme below shows the first steps and the final detachment reaction of a peptide synthesis starting from the carboxyl terminal. N-Boc-glycine is attached to chloromethylated styrene-divinylbenzene copolymer resin. This polymer swells in organic solvents but is completely insoluble. ) Treatment with HCl in acetic acid removes the fert-butoxycarbonyl (Boc) group as isobutene and carbon dioxide. The resulting amine hydrochloride is neutralized with triethylamine in DMF. 

Fig. 30. Synthesis of an acid-labile copolymer by radical copolymerization using a latent HOST, followed by selective deprotection (89).

Synthesis and Properties. Polyquinolines are formed by the step-growth polymerization of o-aminophenyl (aryl) ketone monomers and ketone monomers with alpha hydrogens (mosdy acetophenone derivatives). Both AA—BB and AB-type polyquinolines are known as well as a number of copolymers. Polyquinolines have often been prepared by the Friedlander reaction (88), which involves either an acid- or a base-catalyzed condensation of an (9-amino aromatic aldehyde or ketone with a ketomethylene compound, producing quinoline. Surveys of monomers and their syntheses and properties have beenpubhshed (89—91). 

In 1975, the synthesis of the first main-chain thermotropic polymers, three polyesters of 4,4 -dihydroxy-a,a -dimethylbenzalazine with 6, 8, and 10 methylene groups in the aHphatic chain, was reported (2). Shortly thereafter, at the Tennessee Eastman Co. thermotropic polyesters were synthesized by the acidolysis of poly(ethylene terephthalate) by/ -acetoxybenzoic acid (3). Copolymer compositions that contained 40—70 mol % of the oxybenzoyl unit formed anisotropic, turbid melts which were easily oriented. 

The bulk polycondensation of (10) is normally carried out in evacuated, sealed vessels such as glass ampules or stainless steel Parr reactors, at temperatures between 160 and 220°C for 2—12 d (67). Two monomers with different substituents on each can be cocondensed to yield random copolymers. The by-product sdyl ether is readily removed under reduced pressure, and the polymer purified by precipitation from appropriate solvents. Catalysis of the polycondensation of (10) by phenoxide ion in particular, as well as by other species, has been reported to bring about complete polymerisation in 24—48 h at 150°C (68). Catalysis of the polycondensation of phosphoranimines that are similar to (10), but which yield P—O-substituted polymers (1), has also been described and appears promising for the synthesis of (1) with controlled stmctures (69,70). 

WurtZ-Type Coupling of Dihalosilanes. Several approaches have been developed for the synthesis of polysdanes. However, the most commonly utilized method is based on the Wurtz-type alkah metal coupling of dichlorosilanes. Both homo- and copolymers can be prepared this way (eq. 10). 

Polymerization ofiVIasked Disilenes. A novel approach, namely, the anionic polymerization of masked disilenes, has been used to synthesize a number of poly(dialkylsilanes) as well as the first dialkylamino substituted polysilanes (eq. 13) (111,112). The route is capable of providing monodisperse polymers with relatively high molecular weight M = lO" — 10 ), and holds promise of being a good method for the synthesis of alternating and block copolymers. 

Soluble and weU-characterized polygermane homopolymers, (R Ge), and their copolymers with polysdanes have been prepared by the alkaH metal coupling of diorgano-substituted dihalogermanes (137—139), via electrochemical methods (140), and by transition-metal catalyzed routes (105), as with the synthesis of polysdanes. 

Strong Base Anion Exchangers. As ia the synthesis of weak base anion exchangers, strong base resias are manufactured from styrenic as well as acryhc copolymers. Those based on copolymers of styrene and divinylben2ene are chloromethylated and then aminated. These reactions are the same as for the styrenic weakbase resias. The esseatial differeace is the amine used for amination. Trimethyl amine [75-50-3] N(CH2)3, and /V, /V- dim ethyl eth a n ol amine [108-01 -0] (CH2)2NCH2CH20H, are most commonly used. Both form quaternary ammonium functional groups similar to (8). 

EinaHy, in 1976, Kaminsky and Sinn in Germany discovered a new family of catalysts for ethylene polymerization. These catalysts (ie, Kaminsky catalysts) contain two components a metallocene complex, usually a zkconocene, and an organoaluminum compound, methylaluminoxane (8,9). These catalysts and thek various later modifications enable the synthesis of ethylene copolymers with a high degree of branching uniformity. Formally classified as MDPE, LLDPE, or VLDPE, the resins thus produced have a number of properties that set them apart from common PE resins in terms of performance... 

Gross-Linking. A variety of PE resins, after their synthesis, can be modified by cross-linking with peroxides, hydrolysis of silane-grafted polymers, ionic bonding of chain carboxyl groups (ionomers), chlorination, graft copolymerization, hydrolysis of vinyl acetate copolymers, and other reactions. 

Polymerization using oxygen is not well understood it is known that oxygen copolymerizes with ethylene to form peroxidic copolymers (10). Other free-radical generators such as azo compounds and carbon—carbon compounds have found only limited use in the synthesis of LDPE. 

Most Kaminsky catalysts contain only one type of active center. They produce ethylene—a-olefin copolymers with uniform compositional distributions and quite narrow MWDs which, at their limit, can be characterized by M.Jratios of about 2.0 and MFR of about 15. These features of the catalysts determine their first appHcations in the specialty resin area, to be used in the synthesis of either uniformly branched VLDPE resins or completely amorphous PE plastomers. Kaminsky catalysts have been gradually replacing Ziegler catalysts in the manufacture of certain commodity LLDPE products. They also faciUtate the copolymerization of ethylene with cycHc dienes such as cyclopentene and norhornene (33,34). These copolymers are compositionaHy uniform and can be used as LLDPE resins with special properties. Ethylene—norhornene copolymers are resistant to chemicals and heat, have high glass transitions, and very high transparency which makes them suitable for polymer optical fibers (34). 

The second type of solution polymerization concept uses mixtures of supercritical ethylene and molten PE as the medium for ethylene polymerization. Some reactors previously used for free-radical ethylene polymerization in supercritical ethylene at high pressure (see Olefin POLYMERS,LOW DENSITY polyethylene) were converted for the catalytic synthesis of LLDPE. Both stirred and tubular autoclaves operating at 30—200 MPa (4,500—30,000 psig) and 170—350°C can also be used for this purpose. Residence times in these reactors are short, from 1 to 5 minutes. Three types of catalysts are used in these processes. The first type includes pseudo-homogeneous Ziegler catalysts. In this case, all catalyst components are introduced into a reactor as hquids or solutions but form soHd catalysts when combined in the reactor. Examples of such catalysts include titanium tetrachloride as well as its mixtures with vanadium oxytrichloride and a trialkyl aluminum compound (53,54). The second type of catalysts are soHd Ziegler catalysts (55). Both of these catalysts produce compositionaHy nonuniform LLDPE resins. Exxon Chemical Company uses a third type of catalysts, metallocene catalysts, in a similar solution process to produce uniformly branched ethylene copolymers with 1-butene and 1-hexene called Exact resins (56). 

The additive approach to compatibilization is limited by the fact that there is a lack of economically viable routes for the synthesis of suitable block and graft copolymers for each system of interest. The compatihilizer market is often too specific and too small to justify a special synthetic effort. 

The synthesis of copolymers of olefins with carbon monoxide (eq. 3) or ketones (eq. 4) leads to backbone or side-chain carbonyl functionaUty,... 

The search for new, high performance materials requites the synthesis of weU-defined, narrow molecular weight distribution, cycHc-free, homo- and copolymers. Synthesis of these polymers can be accompHshed by the kinetically controUed polymerization of the strained monomer. 

Divinylbenzene copolymers with styrene are produced extensively as supports for the active sites of ion-exchange resins and in biochemical synthesis. About 1—10 wt % divinylbenzene is used, depending on the required rigidity of the cross-linked gel, and the polymerization is carried out as a suspension of the monomer-phase droplets in water, usually as a batch process. Several studies have been reported on the reaction kinetics (200,201). 

Monomethylacryloyl and vinylbenzyl derivatives of sucrose have been prepared as intermediates for polymers, and preparation of a range of copolymers of styrene and O-methjiacryloylsucrose has been described (114). Synthesis of 4- and 6-0-acryloylsucrose has been achieved by acid-catalyzed hydrolysis of 4,6-0-(l-ethoxy-2-propenyhdene)sucrose (76). These acryloyl derivatives have been polymerized and copolymerized with styrene (qv). 

Vinyl chloride has gained worldwide importance because of its industrial use as the precursor to PVC. It is also used in a wide variety of copolymers. The inherent flame-retardant properties, wide range of plastici2ed compounds, and low cost of polymers from vinyl chloride have made it a major industrial chemical. About 95% of current vinyl chloride production worldwide ends up in polymer or copolymer appHcations (83). Vinyl chloride also serves as a starting material for the synthesis of a variety of industrial compounds, as suggested by the number of reactions in which it can participate, although none of these appHcations will likely ever come anywhere near PVC in terms of volume. The primary nonpolymeric uses of vinyl chloride are in the manufacture of vinyHdene chloride and tri- and tetrachloroethylene [127-18-4] (83). 

The synthesis of his[3-(2-a11y1phenoxy)phtha1imides] and their copolymer properties with BMI have been reported (43). These allylphenoxyimide—BMI copolymers provide toughness and temperature resistance when used in carbon fiber laminates (44). 

Synthetic polymers have become extremely important as materials over the past 50 years and have replaced other materials because they possess high strength-to-weight ratios, easy processabiUty, and other desirable features. Used in appHcations previously dominated by metals, ceramics, and natural fibers, polymers make up much of the sales in the automotive, durables, and clothing markets. In these appHcations, polymers possess desired attributes, often at a much lower cost than the materials they replace. The emphasis in research has shifted from developing new synthetic macromolecules toward preparation of cost-effective multicomponent systems (ie, copolymers, polymer blends, and composites) rather than preparation of new and frequendy more expensive homopolymers. These multicomponent systems can be "tuned" to achieve the desired properties (within limits, of course) much easier than through the total synthesis of new macromolecules. 

Group-Transfer Polymerization. Living polymerization of acrylic monomers has been carried out using ketene silyl acetals as initiators. This chemistry can be used to make random, block, or graft copolymers of polar monomers. The following scheme demonstrates the synthesis of a methyl methacrylate—lauryl methacrylate (MMA—LMA) AB block copolymer (38). LMA is CH2=C(CH2)COO(CH2) CH2. 

The second front originates in the polymer synthesis community. Efforts are mainly directed toward production of monodisperse block copolymers by living polymerizations. These stmctures typically result in microphase separated systems if one block is a high T material and the other is elastomeric in... 

R. P. Quirk, D. J. Kiniiing, and L. J. Fetters, in G. AHen, ed.. Block Copolymers, in Comprehensive Polymer Science The Synthesis, Characterisation, Reactions... 

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