Butadiene Polymerization Methods

Vulcanized rubber compounds are usually reinforced by inorganic filler and/or carbon black to improve the mechanical properties, the thermal stability and the gas barrier properties of the bulky polymer. Carbon black is the most suitable reinforcing agent in the rubber industry thanks to the strong interaction with the polymer matrix. However, due to its polluting nature, the ubiquitous black color of the compounded material and its dependence on petroleum stock pushed the academic and industrially research to look out for other so-called white filler. In this sense, clays seem to be a good choice to replace conventional filler increasing the bulky PB performances. 

Despite the importance of the cis-1,4 PB, 1,2 PB is also an industrially produced polymer which is commonly used in the production of tires, films (packaging breathing items for fruits, vegetables, and seafood), footwear soles, tubes, and hoses. 

The following paragraphs highlight the work concerning the synthesis of 1,3-butadiene based PCNs by in-situ, anionic and spereospedfic, polymerization. 

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Diene polymers refer to polymers synthesized from monomers that contain two carbon-carbon double bonds (i.e., diene monomers). Butadiene and isoprene are typical diene monomers (see Scheme 19.1). Butadiene monomers can link to each other in three ways to produce ds-1,4-polybutadiene, trans-l,4-polybutadi-ene and 1,2-polybutadiene, while isoprene monomers can link to each other in four ways. These dienes are the fundamental monomers which are used to synthesize most synthetic rubbers. Typical diene polymers include polyisoprene, polybutadiene and polychloroprene. Diene-based polymers usually refer to diene polymers as well as to those copolymers of which at least one monomer is a diene. They include various copolymers of diene monomers with other monomers, such as poly(butadiene-styrene) and nitrile butadiene rubbers. Except for natural polyisoprene, which is derived from the sap of the rubber tree, Hevea brasiliensis, all other diene-based polymers are prepared synthetically by polymerization methods. 

An unstable analogue of prostaglandin, PGE, formulated in a poly butadiene polymeric matrix, was placed in a SFE cell and extracted with C02/formic acid (95 5) at 15°C Extraction was continued for 60 min and then the extract was collected in hexane/ethanol (2 1) at 0"C. The advantages of the SFE method were that the solvent effected simultaneous cleavage of the polymer-prostaglandin bond without instability problems and with improved mass transfer enabling good recovery from the polymer matrix. 

The commerical polybutadiene (a highly 1,4 polymer with about equal amounts of cis and trans content) produced by anionic polymerization of 1,3-butadiene (lithium or organolithium initiation in a hydrocarbon solvent) offers some advantages compared to those manufactured by other polymerization methods (e.g., it is free from metal impurities). In addition, molecular weight distributions and microstructure can easily be modifed by applying appropriate experimental conditions. In contrast with polyisoprene, where high cis content is necessary for suitable mechanical properties, these nonstereoselective but dominantly 1,4-polybutadienes are suitable for practical applications.184,482... 

RESINS (Acrylonitrile-Butadiene-Styrene). Commonly referred to as ABS resins, these materials are thermoplastic resins which are produced by grafting styrene and acrylonitrile onto a diene-rubber backbone. The usually preferred substrate is polybutadiene because of its low glass-transition temperature (approximately —80°C). Where ABS resin is prepared by suspension or mass polymerization methods, stereospedfic diene rubber made by solution polymerization is the preferred diene. Otherwise, the diene used is a high-gel or cross-linked latex made by a hot emulsion process. 

Unsaturated rubber polymers are especially important grafting vehicles. Consider, for example, the polymerization of styrene in the presence of l,4-poly(l,3-butadiene). A method consists of dissolving the polybutadiene rubber (about 5 to 10%) in monomeric styrene containing benzoyl peroxide initiator and applying heat. Polymer radicals, formed by (a) chain transfer between the propagating radical and polymer or (b) addition (copolymerization) of the propagating radical to the -double bonds of the polymer. 

In118 carried out by Soviet investigators, the method of mathematical simulation was used to estimate the elementary constants of butadiene polymerization under the conditions of the termination of living chains on impurities. 

FT-NIR spectroscopy in combination with a fiber-optic probe was successfully used to monitor living isobutylene, ethylene oxide and butadiene polymerizations using specific monomer absorptions. In the case of EO a temperature dependent induction period was detected when 5ec-BuLi/ BuP4 were used as an initiating system. This demonstrates the usefulness of this technique because this phenomenon had not been observed so far by other methods. We have also successfully conducted experiments in controlled radical polymerization. Then we were able to monitor the RAFT polymerization of A -isopropylacrylamide (NIPAAm). Thus it can be expected that with the help of online NIR measurements detailed kinetic data of many polymerization systems will become available which will shed more light onto the reaction mechanisms. Consequently, FT-NIR appears to be a method, which can be applied universally to the kinetics of polymerization processes. 

Vinyl monomers such as CH2=CH2 (and others such as CF2=CF2), mono substituted ethylenes CH2=CH(R) (such as propylene, styrene, vinyl chloride, acrylonitrile, methyl methacrylate, etc.), some disubstituted olefins CH2=CRR (such as isobutylene), dienes (such as 1,3-butadiene, isoprene) and also monomers such as acetylene can be polymerized by various polymerization methods to afford linear chain polymers. In all of these po-... 

This chapter aims to give an overview on the recent advances in the synthesis of PCNs through the in-situ 1,3-butadiene homo- and copolymerization technique. To this purpose, we distinguished in-situ polymerization approaches on the basis of the polymerization method anionic or insertion/coordinative. However, before discussing on the topic of this chapter, we wish to briefly recall some peculiar aspects of clay minerals, PNs, and their methods of preparation. 

DCA and apoCA can serve as effective host components for asymmetric inclusion polymerization of prochiral monomers such as 1-substituted butadienes. We reported previously the preparation of optically active polymers with extremely high specific optical rotation of arbitrary sign from (E)- or (Z)-2-methyl-l,3-pentadiene by inclusion polymerization in the canals [7,12-14]. Moreover we have found that butadiene derivatives with polar groups such as cyano or carbomethoxy group can be polymerized to yield optically active polymers. The [ajp values of the resulting polymers were much higher than those of polymers obtained by other known polymerization method. 

Method of synthesis MBS consists of an elastomeric core and a glass shell. The elastomeric core is polybutadiene or styrene-butadiene rubber (SBR), and the shell is poly(methyl methacrylate) and polystyrene. The MBS copolymers are synthesized by emulsion polymerization method. In the preparation process PB polymer or SBR have to be synthesized first and then St and MMAare polymerized on rubber particles. Zhou, C Chen, M Tan, Z Y Sun, S L Ao, Y H Zhang. M Y Yang, H D Zhang, H X, Eur. Polym. J., 42, 1811-18,2006. 

Special polymerization approaches are necessary to prepare random solution SBRs with organolithium in hydrocarbon solvent. The main polymerization methods for producing random copolymers, or containing only short (non-blocky) styrene sequences, are given in Table 5. For convenience, the procedures are divided into those that control the polymerization process in order to maintain a high styrene/butadiene (Bd) ratio in the hydrocarbon media, and those that... 

FIGURE 4.3 Kinetic-heterogeneity distributions of active sites for polymerization of butadiene (1) Method 1 and (2) Method 2. Conversion is 1-3%. 

The kinetic curves for the polymerization of butadiene and isoprene with the titanium catalytic system in the absence of US irradiation (Method 1) are almost coincident (Fig. 4.9). US irradiation (Method 2) brings about an increase in the initial rates of butadiene and isoprene polymerization and accelerates accumulation of the polymer in the system. In this case, the initial rates of polymerization of butadiene and isoprene increase owing to an increase in the rate constant of chain propagation without any marked changes in the concentration of active sites. This result correlates with the estimation of dispersity of the catalytic system, specifically, with the absence of changes in the most probable size of catalyst particles. In the case of polymerization of butadiene via Method 2, the munerical values of rate constants of chain termination increase. 

Polymerization methods for preparing telechelic liquid polymers (TLPs) have been described in the patent and technical literature. An excellent review article by D. M. French on functionally terminated butadiene polymers was published in 1969 [272]. 

It is worthy to note that the first synthetic polybutadiene, produced on a large scale, was obtained by the anionic polymerization method in the presence of metallic sodium. From the names of butadiene and natrium (sodium) it took the trade name Buna. ... 

An unusual method for the preparation of syndiotactic polybutadiene was reported by The Goodyear Tire Rubber Co. (43) a preformed cobalt-type catalyst prepared under anhydrous conditions was found to polymerize 1,3-butadiene in an emulsion-type recipe to give syndiotactic polybutadienes of various melting points (120—190°C). These polymers were characterized by infrared spectroscopy and nuclear magnetic resonance (44—46). Both the Ube Industries catalyst mentioned previously and the Goodyear catalyst were further modified to control the molecular weight and melting point of syndio-polybutadiene by the addition of various modifiers such as alcohols, nitriles, aldehydes, ketones, ethers, and cyano compounds. 

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