Solution polymerization of styrene

Place about 2 mL of dry styrene and 5 mL of xylene in a 25-mL round-bottom flask and add 7 drops of ferf-butyl peroxybenzoate from a Pasteur pipet. Assemble the apparatus for heating under reflux and heat the mixture under reflux for 20 min. Cool the solution to room temperature and then pour about half of it into 25 mL of methanol. Collect the white precipitate of polystyrene that forms by decantation or by vacuum filtration if decantation is not practical. Resuspend the polystyrene in fresh methanol and stir it vigorously. Collect the polystyrene by filtration and allow it to dry in the hood. 

Pour the remaining half of the polystyrene solution onto a watchglass or the bottom of a large Inverted beaker and allow the solvent to evaporate. A clear film of polysfyrene should form. 

Place the filtrate containing a mixture of xylene and methanol in the container for nonhalogenated organic liquids. Flush the methanolic filtrate obtained after resuspension of the polystyrene down the drain. 

Two of the following experiments allow you to explore whether polystyrene is stable toward different organic solvents and to assess the interaction between an ionic polymer, sodium polyacrylate (27), and water. The third lets you investigate the change in the properties of a polymer when it is cross-linked with other strands of itself or other polymers. 

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Reaction Mechanism. The reaction mechanism of the anionic-solution polymerization of styrene monomer using n-butyllithium initiator has been the subject of considerable experimental and theoretical investigation (1-8). The polymerization process occurs as the alkyllithium attacks monomeric styrene to initiate active species, which, in turn, grow by a stepwise propagation reaction. This polymerization reaction is characterized by the production of straight chain active polymer molecules ("living" polymer) without termination, branching, or transfer reactions. 

Fig. 3-19 Continuous solution polymerization of styrene. After Moore [1989] (by permission of Wiley-Interscience, New York).

The use of a precision digital density meter as supplied by Mettler Instruments (Anton Paar, Ag.) appeared attractive. Few references on using density measurements to follow polymerization or other reactions appear in the literature. Poehlein and Dougherty (2) mentioned, without elaboration, the occasional use of y-ray density meters to measure conversion for control purposes in continuous emulsion polymerization. Braun and Disselhoff (3) utilized an instrument by Anton Paar, Ag. but only in a very limited fashion. More recently Rentsch and Schultz(4) also utilized an instrument by Anton Paar, Ag. for the continuous density measurement of the cationic polymerization of 1,3,6,9-tetraoxacycloundecane. Ray(5) has used a newer model Paar digital density meter to monitor emulsion polymerization in a continuous stirred tank reactor train. Trathnigg(6, 7) quite recently considered the solution polymerization of styrene in tetrahydrofuran and discusses the effect of mixing on the reliability of the conversion data calculated. Two other references by Russian authors(8,9) are known citing kinetic measurements by the density method but their procedures do not fulfill the above stated requirements. 

K-Resin SBC synthesis is a batch anionic solution polymerization of styrene and 1,3-butadiene using an n-butyllithium (NBL) initiator in a process referred to as living polymerization . Although often referred to as a catalyst, each NBL gives rise to a distinct polymer chain. Polymer chains grow by adding monomer... 

Solution polymerization of styrene employs a reactor train of polymerization vessels, usually three, each progressively hotter than the first. A stream of about 10% styrene dissolved in ethylbenzene plus a suitable thermally activated initiator, is fed into the first reactor under an inert atmosphere and kept at 110-130°C. The solution moves through each reactor in turn until it leaves the last reactor at 150-170°C, the polymerization at this point being completed to the extent desired (Eq. 23.6). 

Consider the isothermal solution polymerization of styrene at 60°C in the following formulation ... 

SBR may also be produced by anionic solution polymerization of styrene and butadiene with alky-llithium initiator (e.g., butyllithium) in a hydrocarbon solvent, usually hexane or cyclohexane. In contrast to emulsion SBR, which may have an emulsifier (soap) content of up to 5% and nonrubber materials sometimes in excess of 10%, solution SBR seldom has more than 2% nonrubber materials in its finished form. Solution SBR has a narrower molecular weight distribution, higher molecular weight, and higher cis-1,4-polybutadiene content than emulsion polymerization SBR. 

The use of these reagents does not detract from the efficiency of the RAFT process and values of up to 33,000 with PDI values of 1.04 to 1.07 have been obtained for bulk and solution polymerization of styrene, methyl methacrylate, and n-butyl acrylate. 

Among other sieves XY mordenite in the H form initiate the solution polymerization of styrene. Interestin y, the system is believed to result in the formation of polymeric molecular sieves with altered ion exchange and molecular adsorption characteristics. 

The free radical polymerization of vinyl monomers should benefit from the excellent heat transfer and mixing speed of micro-reactors. When Hessel et al. [15] investigated, for the first time, the use of a micro-reactor in a free radical polymerization, they modeled the outcome of a solution polymerization of styrene as a monomer and azobisisobutylonitrile (AIBN) as an initiator for three different micro-reactor types [16], the aim being to compare the effects of micro-reactor... 

Figure 2.9. Simplified flow diagram for solution polymerization of styrene.

The early studies demonstrated the possibility of initiating polymerization by intensive mechanical dispersion of certain inoiganic substances, including metals (Fe, Al, Mg, Cr, W) in vinyhc monomers. The degree of polymerization of styrene, vinyl acetate, acrylonitrile, or MMA depended on the dispersion intensity. The fresh metal surfaces play the role of catalyst and initiator. These surfaces are the sites of electron transfer from the surfaces metal atoms to the monomers to form ion-radical initiating particles. Colloidal particles of Au, Tl, and Pt were found to influence substantially the bulk and solution polymerization of styrene. - ... 

Compare bulk and solution polymerization of styrene. Use a 20% styrene (by mass) in the solution. Assume that the Cp values for both styrene and the solvent are 2.09 J/g K. 

Various inhibitors have been used in new determinations of rates of initiation in bulk polymerizations of acrylonitrile " and solution polymerizations of styrene an improved procedure has been proposed.Aromatic aldonitrones, polymers with attached t-butyl nitroxide groups and charge-transfer complexes of anthracene have been studied as inhibitors. 

Salehpour S, Duhe MA, Murphy M. Solution polymerization of styrene using biodiesel as a solvent effect of biodiesel feedstock. Can J Chem Eng 2009 87 129-135. 

The alternative method of Bauduin et based on the evolution of DPn with monomer conversion p has also been used (eqn [9]). (This method holds for low values of Cm, typically Cmvalue approaches DPn = [M]oXp/[CTA]o from low monomer conversion and therefore this method is not suited to calculate Ctrl in this case.) For instance, Teodorescu applied this method to determine Ctrl - 0. 46 for the transfer agent vinyliodoacetate (CH2=CH0C(0)CH2-I) in the solution polymerization of styrene in benzene at 60 ° C with AIBN initiator. 

The polymerization of styrene in solution [53,58] and bulk [54,55,59—61] by the redox system benzoyl peroxide-di-n-alkylaniline has been studied considerably by many researchers. Different dialkylanilines (DAAs) such as dimethylaniline (DMA), diethylaniline (DBA), di-n-butylanilines, di-n-oc tylaniline, and di-n-decylaniline combined with benzoyl peroxide have been studied for the solution polymerization of styrene [58] in benzene at 30 C. It was found that the initial rate of polymerization increased with a decrease of the molar ratio of BZ2O2/DAA for a specific concentration of monomer and BZ2O2. The degree of polymerization decreased with the decrease of molar ratio of BZ2O2/DAA. The initiator efficiency seemed to increase gradually with the number of carbons of the alkyl groups in the DAAs, with the exception of di-n-octylaniline. 

In solution polymerization of styrene, the viscosity of the polymerizing solution is much lower than in the mass process thus, temperature control is easier. Ethyl benzene is the most commonly used solvent and its concentration in the feed stream is about 5-25%. After polymerization, unreacted styrene and solvent are removed from the polymer and recycled. Three reactor types are used for solution polymerization of styrene as shown in Fig. 5 [22]. 

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