fhe free radical polymerization of styrene in benzene was studied theoretically and experimentally over ranges of monomer and catalyst (AIEN) concentrations and temperature in an isothermal, stirred batch reactor. Molecular weight distributions were measured with a gel permeation chromatograph. Tung's hermite polynomial method was used to correct for imperfect resolution.The differential rate equations have been solved to predict the conversion of monomer and molecular weight distribution of the polymer as a function of time. These solutions were used to interpret the experimental rate data.Good agreement between theory and experiment was found for narrow and broad distribution, provided the variation of the termination constant with solvent concentration was accounted for.The agreement between the experimental and calculated molecular weight distribution suggests the utility of gel pemeation chroma'tography in the investigation of polymer reaction kinetics.The kinetic mechanisms of free radical polymerization of vinyl monomers in solution have been well established for small conversions of monomer ( 1 ) . This is not so for large conversions. In many instances the resultin differential weight distribution as a function of time. Amundson (2) has solved the equations describing several of these mechanisms. However, until now, experimental verification of these mechanisms has not been attempted due to the tedious nature of the available methods for measuring molecular weight distribution. The recent development of the gel permeation chromatograph ( 3 ) , which allows the rapid measurement of molecular weight distribution, has made such a verification possible. The present investigation has exploited the use of the gel permeation chromatograph (GPC) and digital computer to this end. equations have not been solved to predict t 5 e molecular THEORYThe following steps describe the mechanism of solution polymerization using a free radical catalyst ( AIBN) that has been investigated in the present study:Initiation:rate constant kf, rate constant kfR," + R," + P,+ , RT" + R," + P, + P , rate constant kt,In these equations R," represents one of two identical free radical fragments formed in the decomposition of the catalyst; R, " represents a polymer radical comprising r monomer units, S is a solvent, and M is a monomer molecule, while P, represents a dead polymer molecule containing r monomer units. In the development of the differential rate equations it is assumed that only the above reactions take place. Furthermore, it is assumed that the solvent and monomer radicals formed in the chain transfer

An investigation was made of the simulation of bulk and solution polymerization of styrene in a continuous stirred-tank reactor (CSTR). A theoretical model from the literature was usad to predict conversion, molecular weight distribution (MWD), and molecular weight averages. The kinetic rate constants required to solve the model were also taken from the literature.Styrene Commercial production of a new polymer is generally preceded by several stages of laboratory-scale and pilotplant production and testing to overcome problems associated with scale-up. Two objectives are to produce a product of a desired specification and to maximize its yield (or minimize its cost). The savings which could be realized by reducing pilot-plant production and testing provide a real incentive for investigating the design, simulation, and optimization of polymerization reactors.Considerable work has been done on the theoretical description of polymerization reactors (1 to 14), but little experimental work has been done to check the theoretical models (10 to 141, due, until recently, to the lack of a rapid technique for measuring molecular weight distribution. The object of this investigation was to test the validity of a theoretical model for the bulk and solution polymerization of styrene.This investigation is concerned with the simulation of a bench-scale, continuous, stirred-tank reactor (CSTR) in which monomer conversion and polymer molecular weight distribution (MWD) were used as criteria of simulation. Conversion was chosen since it is a measure of yield and MWD was chosen since many of the important physical properties of the polymer are determined by it. The solution polymerization of styrene (benzene as solvent) was chosen for study since its reaction mechanism has been relatively well established at low conversions (15) and the required rate constants are available in the literature (15to23).The mass balance equations were solved to predict conversion and MWD. Experimental olymerizations in a CSTR over a range of reaction con&ions yielded experimental conversions and MWD's which were compared with the theoretical results.The recently developed gel permeation chromatogra h distribution. This relatively rapid technique and the availability of a high-speed digital computer (IBM 7040) for solving the theoretical model have made this investigation feasible.art of a larger study, which includes development wor ! on gel permeation chromatography and polymerization studies in batch reactors (28). THEORYIn the development of the theoretical model the assumptions made were: mixing is perfect, reactor is operating at steady state, kp and kt are independent of polymer radical chain length, termination is by combination only, all radicals have the same reactivity, and no density change occurs in the reactor.The kinetic mechanism selected for the theoretical model is from Bamford et al. (15). It includes transfer to monomer and solvent.

Measureme~lts of the absorption spectra were made on solutions of allcali and allcaline earth metals in ammonia, methylamine, ethylarnine, and ~nixecl solvents. I n ammonia, a single absorption band was measured which is common to all the ~netals esamined. I n the arnines and in mixtures of arnlno~~ia mith methylamine, ho~vever, bands were found which were characteristic of the metal employed. h hypothesis has been advanced to explain the existence of the different types of energy traps responsible for the variations in spectra.The alliali metals ancl some of the a l l d i n e earth metals dissolve in liquid ammonia without reaction; it is thought that simple dissolution occurs, yielding metal ions and electrons xxrl~ich are trapped or solvated in the liquid (5). Various physical properties have been examined whiclz are consistent mith this postulate, although a concise model has not yet been formulated for the electron traps. For example, the expansion exhibited on dissolving the metal has been attributed t o the formation of holes in the liquid which represent energy barriers for the escape of electrons (8). The electrical conductivity in dilute solution is greater than can be explained by simple ionic transport, but less than mould be expected by electronic conduction (5). Magnetic susceptibility measurements indicate that the metal is ionized, but some difficulty is experienced in explaining the variation of the susceptibility with temperature (3). The measurements of paramagnetic resonance absorption are consistent with the existence of trapped electrons (4). Finally, the absorption spectra of a number of the solutions have been measured, and the observation made that in ammonia there is a single absorption maximum whose position is independent of the particular metal in solution (1, 9). This maximum is in a region where none appears in the spectrum of bullr sodium metal; ancl in the spectrum of atomic sodium, very strong absorption occurs a t 5889 i % (D line), which does not appear in the solution spectrum. Since the maximum observed is also absent from the spectrum of sodium ion and of liquid ammonia, it has been ascribed t o the trapped electrons.Primary amines will also dissolve some of the metals; sodium, cesium, potassium, lithium, and calcium are soluble in methylamine, ~vhile ethylarnine dissolves a t least lithium and potassium. Although these solutions have been exaininecl lcss exhaustivelj. than the ammonia solutions, their behavior is similar. Thus the variation of electrical conductivity with concentration in metal solutions in methylamine is similar t o that in anhydrous alnmonia (2), and the absorption spectra, although exhibiting maxima a t a different wave l11hnzrscript

Hg (63P1) at room temperature and at 300 °C. and Hg (61P1) at room temperature fail to react with carbon tetrafluoride at a measurable rate. Xe (3P1) causes carbon tetrafluoride to decompose with a quantum efficiency of about unity to yield fluorine and an unidentified solid product. It is concluded that the energy necessary to break the first C–F bond m CF4 is more than 154 and less than 194 kcal. per mole. Hydrogen atoms produced from Hg (63P1) at room temperature and at 300 °C. and from Hg (61P1) at room temperature do not react with carbon tetrafluoride. It is concluded from this that the activation energy of the reaction CF4 + H → CF3 + HF is not less than 14 kcal. per mole.

Trifluoromethyl radicals were produced by the reaction between atomic sodium and iodo-, broino-, and chloro-trifluoromethane in the diffusion flame apparatus. The results indicate that:(1) The primary reaction is CFXX + Na -+ NnX + CF3.(2) For the reaction between sodium and iodo-, bromo-, and chloro-trifli~oro-methane, the activation energy is 1.7, 2.3, and 7.4 kcal. per mole, respectively.(3) Some decomposition of trifluoromethyl radicals occurs, yielding chiefly tetrafluoroethylene.(4). Reaction occurs between molecular hydrogen and trifluoromethyl radicals yield~ng fluoroforln.