Random copolymers preparation

Production of OBCs by chain shuttling catalysis can result in a copolymer with a melting point more than 50 °C higher than that expected for a statistically random copolymer prepared at equivalent density. Figure 17 shows the typical relationship between density and melting point for random ethylene-LAO copolymers. The circled symbols are several OBCs prepared by chain shuttling catalysis [10]. While a typical random copolymer with density of 0.88 g cm-3 would melt at 60 °C, the OBCs made by chain shuttling do not melt until almost 120 °C. 

Solution random copolymers prepared by the above procedures have performed well in tire-tread formulations. 22 They require about 20 percent less accelerator (see Table II) as compared to an emulsion SBR and give higher compounded Mooney, lower heat buildup, increased resilience and better retread abrasion index. 

The homopolymer of DMP dissolves readily in methylene chloride but precipitates on standing as a crystalline polymer-CH2Cl2 complex, providing a method for distinguishing between block copolymers and mixtures of homopolymers. Random copolymers prepared by methods a and b form stable solutions in methylene chloride. Copolymers with a 1 1 ratio of DMP and DPP prepared by methods c and d also yield stable methylene chloride solutions. Since the NMR spectrum shows that the DMP portion of these materials is present as a block and the solubility in methylene chloride shows that DMP homopolymer is absent, these copolymers have the block structure. They can be separated by crystallization from m-xylene into an insoluble DPP-rich fraction and a soluble DMP-rich fraction, both fractions having the NMR spectra characteristic of block copolymers. A typical 1 1 copolymer prepared by adding DMP to growing DPP polymer yielded 35% of insoluble material... 

Top block copolymer prepared by Procedure 2 Center random copolymer prepared by Procedure 1 Bottom a blend of homopolymers... 

Aldol group transfer polymerization of ferf-butyldimethylsilyl vinyl ether [62] was initiated by pendant aldehyde functions incorporated along a poly(methyl methacrylate) (PMMA) backbone [63]. This backbone was a random copolymer prepared by group transfer polymerization of methyl methacrylate (MMA) and acetal protected 5-methacryloxy valeraldehyde. After deprotection of the aldehyde initiating group, polymerization proceeded by activation with zinc halide in THF at room temperature. The reaction led to a graft copolymer with PMMA backbone and poly(silyl vinyl ether) or, upon hydrolysis of the ferf-butyldimethylsilyl groups, poly(vinyl alcohol) branches. 

Besides these random copolymers prepared by solution polymerization, those obained by bulk polymerization and block copolymers were also used for the application examples. 

The success of the living-radical polymerization field will be defined on the basis of the commercialization of any of these processes [48], It is believed that the strength of the living-radical polymerization systems lies in their ability to make polymers of novel architecture, for example, block copolymers. However, very little work has been done to look at the properties of materials prepared by these processes. It remains to be seen whether block copolymers, prepared by living-radical polymerization processes, have any performance advantages over random copolymers prepared by conventional free-radical polymerization. 

Random copolymers of styrene/isoprene and styrene/acrylonitrile have been prepared by stable free radical polymerization. By varying the comonomer mole fractions over the range 0.1-0.9 in low conversion SFRP reactions it has been demonstrated that the incorporation of the two monomers in the copolymer is analogous to that found in conventional free radical copolymerizations. The composition and microstructure of random copolymers prepared by SFRP are not significantly different from those of copolymers synthesized conventionally. These two observations support the conclusion that the presence of nitroxide in the SFR process does not influence the monomer reactivity ratios or the stereoselectivity of the propagating radical chain. Rather, the SFR propagation mechanism is essentially the same as that of the conventional free radical copolymerization process. 

Syntheses of PVBT-co-PBMA (poly(vinylbenzylthymine-co-butyl methacrylate) [T-PBMA]) and PVBA-co-PS (poly(vinylbenzyladenine-co-styrene) [A-PS]) random copolymers prepared through free radical polymerization. (Reprinted with permission from Kuo, S. W., and Cheng, R. S. 2009. DNA-like interactions enhance the miscibility of supramolecular polymer blends. Polymer 50 177-188. Copyright 2009, Elsevier Science Ltd., UK.)... 

The tacticity of the random copolymers prepared by living free radical polymerization is also found to have the same sequence distribution and tacticity as those prepared by normal free-radical methods. Besides low polydispersities, another advantage of living free radical polymerization is that the chain ends can be controlled to a degree previously only obtainable with more demanding techniques. In one example, a pyrene-ended styrene-methyl methacrylate copolymer (VI) was prepared by living free radical polymerization using the unimolecular initiator (V), which in turn was prepared by esteri cation of pyrene-1-butyryl chloride with (IV) in the presence of 4-(dimethylamino)pyridine (see Fig. 11.9). 

Calafel Itxaso, Munoz Marfa Eugenia, Santamarfa Anton, Boix Miquel, Conde Jose Ignacio, and Pasqual Belen. PVC/PBA random copolymers prepared by hving radical polymerization (SET-DTLRP) Entanglements and chain dimensions. Eur. Polym. J. 73 (2015) 202-211. 

Table 2 Random Copolymers Prepared by GTP (Initiator MTS Catalyst TASHF2) Monomers...

Styrene-butadiene rubber is prepared from the free-radical copolymerization of one part by weight of styrene and three parts by weight of 1,3-butadiene. The butadiene is incorporated by both 1,4-addition (80%) and 1,2-addition (20%). The configuration around the double bond of the 1,4-adduct is about 80% trans. The product is a random copolymer with these general features ... 

Many random copolymers have found commercial use as elastomers and plastics. For example, SBR (62), poly(butadiene- (9-styrene) [9003-55-8] has become the largest volume synthetic mbber. It can be prepared ia emulsion by use of free-radical initiators, such as K2S20g or Fe /ROOH (eq. 18), or in solution by use of alkyl lithium initiators. Emulsion SBR copolymers are produced under trade names by such companies as American Synthetic Rubber (ASPC), Armtek, B. F. Goodrich (Ameripool), and Goodyear (PHoflex) solution SBR is manufactured by Firestone (Stereon). The total U.S. production of SBR in 1990 was 581,000 t (63). 

A living cationic polymeriza tion of isobutylene and copolymeriza tion of isobutylene and isoprene has been demonstrated (22,23). Living copolymerizations, which proceed in the absence of chain transfer and termination reactions, yield the random copolymer with narrow mol wt distribution and well-defined stmcture, and possibly at a higher polymerization temperature than the current commercial process. The isobutylene—isoprene copolymers are prepared by using cumyl acetate BCl complex in CH Cl or CH2CI2 at —30 C. The copolymer contains 1 8 mol % trans 1,4-isoprene... 

As has been described in Chapter 4, random copolymers of styrene (St) and 2-(acrylamido)-2-methylpropanesulfonic acid (AMPS) form a micelle-like microphase structure in aqueous solution [29]. The intramolecular hydrophobic aggregation of the St residues occurs when the St content in the copolymer is higher than ca. 50 mol%. When a small mole fraction of the phenanthrene (Phen) residues is covalently incorporated into such an amphiphilic polyelectrolyte, the Phen residues are hydrophobically encapsulated in the aggregate of the St residues. This kind of polymer system (poly(A/St/Phen), 29) can be prepared by free radical ter-polymerization of AMPS, St, and a small mole fraction of 9-vinylphenanthrene [119]. 

Dall Asta and Motroni (44, 57) provided direct experimental evidence for the transalkylidenation mechanism in the case of cycloalkenes. With a catalyst system consisting of WOCI4, C2H6A1C12, and benzoyl peroxide they prepared a random copolymer of cyclooctene and cyclopentene, the cyclo-pentene double bond being labeled with 14C. The distribution of the radioactivity in the copolymer formed will depend on the site of ring opening. 

The latter equahon may also be used to predict the approximate of a random copolymer, using the mass fractions of the respective monomers from which the copolymer was prepared. 

Coordination polymerization is the most versatile method of preparing PCL and its copolymers, affording high molecular weights and conversions, and either block or random copolymers depending on the conditions. As with the preceding classes of initiators, the product... 

This feature of the interfacial preparation of poIy(iminocarbon-ates) has an important consequence for the synthesis of copolymers if the dicyanate component is structurally different from the diphenol, partial hydrolysis of the dicyanate will lead to the presence of two structurally different diphenol components that will compete for the reaction with the remaining dicyanate. The interfacial copolymerization will therefore result in a random copolymer. On the other hand, during solution polymerization no hydrolysis can occur. Since the dicyanates can only react with diphenols and vice versa, solution polymerization results in the formation of a strictly alternating copolymer. 

Since the late 1940s, NCA polymerizations have been the most common technique used for large scale preparation of high molecular weight polypeptides [13]. However, these materials have primarily been homopolymers, random copolymers, or graft copolymers that lack the sequence specificity and monodispersity of natural... 

Polystyrene is unusual among commodity polymers in that we can prepare it in a variety of forms by a diversity of polymerization methods in several types of reaction vessel. j Polystyrene may be atactic, isotactic, or syndiotactic. Polymerization methods include free radical, cationic, anionic, and coordination catalysis. Manufacturing processes include bulk, solution, suspension, and emulsion polymerization. We manufacture random copolymers ... 

In 1968, a French Patent issued to the Sumitomo Chemical Company disclosed the polymerization of several vinyl monomers in C02 [84], The United States version of this patent was issued in 1970, when Fukui and coworkers demonstrated the precipitation polymerization of several hydrocarbon monomers in liquid and supercritical C02 [85], As examples of this methodology, they demonstrated the preparation of the homopolymers PVC, PS, poly(acrylonitrile) (PAN), poly(acrylic acid) (PAA), and poly(vinyl acetate) (PVAc). In addition, they prepared the random copolymers PS-co-PMMA and PVC-co-PVAc. In 1986, the BASF Corporation was issued a Canadian Patent for the preparation of polymer powders through the precipitation polymerization of monomers in carbon dioxide at superatmospheric pressures [86], Monomers which were polymerized as examples in this patent included 2-hydroxyethylacrylate and iV-vinylcarboxamides such as iV-vinyl formamide and iV-vinyl pyrrolidone. 

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