Free-radical Homopolymerization Research Articles

Synthesis and polymerization of chiral monomers containing dimethylaminobornane moieties

AbstractChiral monomers (cis, endo‐3‐dimethylamino‐2‐bornyl methacrylate (DABM) and N, N‐dimethyl[cis,endo‐2‐(2‐vinyloxyethoxy)‐3‐bornyl]amine (DVEBA)) were synthesized from (+)‐camphor. The free radical homopolymerization of both DABM and DVEBA, and the copolymerization of both chiral monomers with achiral methyl methacrylate and styrene, resp., were carried out in various organic solvents. Effects of temperature, solvents, and reaction time on the polymerizations were studied. Dependences of the specific rotation of the chiral copolymers on the feed concentration and reaction conditions were investigated. Application of the chiral polymers on the asymmetric induction were also investigated.

Effect of chain transfer agent and the reaction medium on the limiting conversion of methyl methacrylate free radical polymerization

The kinetics of free radical homopolymerization of methyl methacrylate in the presence of n-dodecyl mercaptan have been studied at 70° in bulk, using a 3 mol/l solution in benzene. The results indicate that, when the polymerization is carried out in solution, the chain transfer agent does not influence the overall rate of polymerization or the limiting conversion. Also, in bulk polymerization, the presence of n-dodecyl mercaptan does not significantly modify the limiting conversion when polymer is isolated by lyophilization. For the bulk polymerization, the differences in both molecular weight and limiting conversion, when polymers are isolated by lyophilization or by precipitation, have been qualitatively correlated with current theories on free radical polymerization at high conversion.

A mathematical model of mixing and polymerization in a semibatch stirred‐tank reactor

AbstractEffects of mixing on number‐ and weight‐average degree of polymerization in free radical homopolymerization in solution in a semibatch stirred tank‐reactor have been modeled by use of the “partially segregated feed” model of Villermaux (1989) and the lumped kinetic treatment of addition polymerization. Mixing conditions are described in terms of the dimensionless time constants θM and θX for convective and diffusive mixing, respectively. Results show that DPn is relatively insensitive, while DPw is highly sensitive to mixing conditions. Comparison with ideal mixing results shows that polydispersity (DPw/DPn) can rise greatly as mixing becomes increasingly nonideal, depending on the value of dimensionless flow rate and dimensionless initiator rate constant. Time constants of the mixing model need to be expressed as dimensional correlations before the proposed polymerization model can be compared to experimental measurements. The model may be adapted to melt polymerization in nonideal CSTR such as LDPE.

Homopolymerization and copolymerization of 1-phenylsulfonylbicyclobutane

1-Phenylsulfonylbicyclobutane (SBB) undergoes free radical homopolymerization to give soluble homopolymers, but attempted anionic homopolymerizations did not succeed. With free radical initiators, SBB copolymerizes with p-methoxystyrene, p-methylstyrene, methyl methacrylate, acrylonitrile and 1-cyanobicyclobutane to yield novel copolymers. The reactivity of SBB toward vinyl monomers is lower than that of 1-cyanobicyclobutane.

Development of a unified mathematical framework for modelling molecular and structural changes in free-radical homopolymerization reactions

In the present study, a unified mathematical framework is developed for modelling molecular and structural changes in free-radical homopolymerization reactions. Three modelling methods — namely, the instantaneous property method (IPM), the method of moments (MM) and a new hybrid method, the so-called property moments method (PMM) — are derived using a unified approach. A critical analysis is carried out to determine the conditions under which each of the above methods can be applied to a given polymerization system. This is achieved through the application of the three modelling methods to several experimentally investigated free-radical polymerization systems leading to linear and branched polymers. Polymerizations are examined in bulk and in solution, both in the presence and in the absence of strong diffusional limitations in the termination and propagation reactions.

Characterization of the free-radical homopolymerization of N-methylmaleimide

Etude par RPE de la polymerisation radicalaire amorcee par bombardement d'hydrogene atomique du N-methyl maleimide, compose modele de resines thermodurcissables a base de bis-maleimide. Identification de 3 types de radicaux intervenant aux differentes etapes de la polymerisation

Radical copolymerization of 3‐tri‐n‐butylstannylstyrene with several vinyl monomers

AbstractThe free radical homopolymerization and copolymerization of 3‐tri‐n‐butylstannylstyrene (3‐BTS) with styrene (ST), ethyl acrylate (EA), methyl methacrylate (MMA), vinyl acetate (VA), and acrylonitrile (AN) were carried out using 2,2′‐azobisisobutyronitrile (AIBN) at 60°C. It was found that the yield of conversion to poly(3‐BTS) increased with the molar ratio of initiator to monomer as well as with polymerization time. The conversion at equilibrium after 50 h was about 40%. The compositions of copolymer samples were determined from elemental analyses. Monomer reactivity ratio and Q‐e values were calculated. The copolymers of 3‐BTS‐MMA and 3‐BTS‐AN were found to be alternating. The copolymers of 3‐BTS with MMA, EA and AN were not soluble in any of a large number of organic solvents tested. The insolubility is believed to be due to formation of intermolecular coordination among the tributylstannyl moiety and the carbonyl or cyano groups of the polymer. These copolymers, however, were “soluble” in trihaloacetic acid, but this solubility was due to a cleavage of the trialkyltin moiety from the phenyl groups. The glass temperatures, Tg, and melting temperatures Tm, of the various polymers were also studied.

Synthese de polyacrylates dithiocarboxyliques—II. Homo et copolymerisation d'acrylates fonctionnalises

Free radical homopolymerization of thiocarboxylic acrylates leads to high polymers in high yield. This behaviour differs greatly from that of its dithiocarboxylic counterparts which show low reactivity in homopolymerization; copolymerizations are possible and several tests with sulphurated acrylates and with the usual comonomers have allowed calculation of the Alfrey-Price parameters ( e, Q) and of reactivity ratios. These acrylates complete the range of the dithiocarboxylic monomers, study of which has led to a new class of highly reactive functionalized polymers.

The multiple-component initiator technique for constant-rate free-radical homopolymerization

The multiple initiator method of controlling polymerization at a prescribed rate is studied. A correlation of the auto-acceleration function with the kind and concentration of the initiator is assumed. The equations for the determination of the kind and concentration of the initiator to control polymerization at a constant rate are then derived. Bulk polymerization of methyl methacrylate is chosen for verification. Using the method proposed and binary initiator systems, we determine several sets of initiator pairs and their concentrations for polymerization of methyl methacrylate at rates of 0.1 and 0.2 h −1 for various reaction temperatures. The results indicate that the polymerization rates obtained with the given initiator pairs and concentrations are what we have prescribed.

Anionic Copolymerization of Elemental Sulfur with Propylene Sulfide. Equilibrium Sulfur Concentration

Abstract In the anionic copolymerization of elemental sulfur (S8) with propylene sulfide (P) below the floor temperature of elemental sulfur homopolymerization (Tf = 159°C), there is a certain concentration of elemental sulfur left when copolymerization is completed ([S8]eq). The dependence of [S8]eq on the feed ratio [P]0/[S8]0 and temperature was determined by using laser Raman spectroscopy, and this enabled us to distinguish between the S-S bonds in elemental sulfur and in the linear polysulfide. [S8]eq was found to decrease with increasing temperature and with an increasing [P0]/[S8]0 ratio. The experimental dependence of the average enthalpy and entropy of polymerization (δ[Hbar][Xbar], and δ [Sbar][Xbar]) on [Xbar], as described by the equilibrium …-CH2CH(CH3)SX − + S8 = …-CH2CH(CH3)SX+8 −, has shown that at [Xbar] ⇋; 9 the experimental δ[Hbar][Xbar] and δ [Sbar][Xbar] approach values determined earlier for the free radical homopolymerization of elemental sulfur …-Sn • + S8 ≤ …-S• n+8& The corresponding values are 3.1 kcal/mol and 4.76 cal/mol · degree.

RECENT DEVELOPMENTS IN FREE RADICAL POLYMERIZATION AT HIGH CONVERSION—DIFFUSION CONTROLLED TERMINATION AND PROPAGATION

Abstract A deeper understanding of the dynamics of macromolecules in polymer melts (reptation theory—de Genne and others refer to PVC-Cleveland on long term aging of glassy polymers) has sparked a number of investigations on the modelling of the termination and propagation reactions in free radical homopolymerization. These recent contributions will be reviewed and some statements will be made about limitations of the present models and recommendations will be made for future study.

Preparation, polymerization and copolymerization of some unsaturated dibutyltin carboxylates

Dibutylchlorotin acrylate (DBCTA), dibutylchlorotin methyl maleate (DBCTM) and dibutylchlorotin cinnamate (DBCTC) were prepared by metathesis reactions between equimolar proportions of dibutyltin dichloride and the corresponding dibutyltin dicarboxylate. The acrylate (DBCTA) was the only monomer to undergo free-radical homopolymerization and gave an insoluble cross-linked polymer of poly(dibutyltin diacrylate) with the expulsion of dibutyltin dichloride. Free-radical copolymerization with methyl acrylate (MA) gave copolymers with DBCTA and DBCTC. The reactivity ratios were respectively: MA, r 1 = 0.81 ± 0.05; DBCTA, r 2 = 0.08 ± 0.04 and MA, r 1 = 2.0 ± 0.35 DBCTC, r 2 = 0 ± 0.2. DBCTM did not copolymerize with methyl acrylate. Attempts at free-radical copolymerizations with vinyl chloride (VC) were only partially successful due to severe inhibition. DBCTM and DBCTC formed very low molecular weight copolymers containing approximately equal amounts of the comonomers. DBCTA copolymer with VC formed a copoly(dibutyltin diacrylate) network structure. However, solubility in acetic acid-d 4 due to an exchange equilibrium allowed an estimate of the reactivity ratio r vc ≌ 0.17 to be obtained by NMR analysis. Three new tetrabutyl-1,3-di(carboxy) distannoxanes ([Bu 2SnOCOR] 2O) ( R = CHCH 2; C(CH 3)CH 2 and CHCHC 6H 5) were prepared.

Polymerization of vinyl monomers in the presence of the ethylaluminium dichloride‐p‐chloranil catalytic system

AbstractPolymerizations of acrylonitrile, methacrylonitrile, methyl acrylate, and methyl methacrylate initiated by the system ethylaluminium dichloride (EtAlCl2)‐p‐chloranil (PClA) were studied. The effect of the catalyst system components on the initiation, propagation and termination steps is discussed in terms of a free radical reaction mechanism. The catalytic system EtAlCl2‐PClA behaved similarly in the copolymerization of MMA with styrene as in the free radical homopolymerization of MMA. Polymerizations of vinyl monomers, not forming relatively stable complexes with EtAlCl2 (in contrast to acrylic and methacrylic monomers), such as vinyl chloride, styrene and isobutylene, were also studied in the presence of the EtAlCl2‐PClA system.

Stereo- and regio-selective formation of 2-oxazolone telomers as potential synthetic intermediates for aminosugars

3-Acetyl-2-oxazolone readily undergoes free-radical homopolymerization as well as telomerization with polyhalomethanes, in which low telomer formation is highly stereo- and regio-selective.

Control of Batch Polymerizations by Continued Feed

Abstract The conventional kinetic scheme for a free-radical homopolymerization is modified to incorporate dilution by a feed stream and the effect of propagation on solution density. Neglect of the volume change can result in prediction of erroneously high conversions. The distribution of average molecular weight fractions is evaluated. In the absence of gelation and transfer reactions, the broadening, which is usually thought to arise from varying composition, is found to be small compared to that which is intrinsic to the addition mechanism.

Free radical chain transfer to allyl monomers at low polymerization temperatures

AbstractAlkylboron–oxygen, an active, low‐temperature free radical initiator, has been employed to investigate the effects of very low polymerization temperatures on the free radical homopolymerization and copolymerization of allyl monomers. Unlike some polymerizations which have been reported to undergo dramatic changes in polymerization rates at very low polymerization temperatures, the allyl systems behaved in a like manner at high and low temperatures. Similar, low values of reduced viscosities were obtained for homopolymers of allyl monomers prepared over a 300°C. temperature range. An almost identical effect of allyl chloride concentration on the molecular weight of ethyl acrylate/allyl chloride copolymers was also observed for copolymerizations performed over a 100°C. temperature range. For solution homopolymerizations and copolymerizations the activation energy for free radical abstraction from the allyl monomer is, therefore, nearly equal to the activation energy for addition of that radical to the allyl double bond, even at temperatures down to the melting points of the monomers.

Free radical homopolymerization and copolymerization of vinyl phosphines, oxides, and sulfides

AbstractA variety of free radical catalysts failed to homopolymerize diphenylvinylphosphine and diisobutylvinylphosphine oxide. Oligomeric products were obtained with diphenylvinylphosphine oxide and sulfide. It was shown that in the homopolymerization of the oxide at 100 and 130°C., the molecular weight is independent of catalyst concentration. Further a minimum kinetic chain length for the 0.10 mole‐% di‐tert‐butyl peroxideinitiated bulk polymerization at 130°C. was calculated to be 500 units. Reactivity ratios with styrene and methyl methacrylate (MMA) were obtained from copolymerization data (phosphorus monomer is M2). The following r1 values were obtained (all r2 values were close to zero): with diphenylvinylphosphine sulfide: styrene (2.1 ± 0.3), MMA (13 ± 3); with diphenylvinylphosphine oxide: styrene (5 ± 1), MMA (11 ± 4); with diphenylvinylphosphine: styrene (7 ± 1), MMA (5.1 ± 0.2); with diisobutylvinylphosphine oxide: styrene (17 ± 5), MMA (30 ± 10). It was concluded that the phosphorus groups do not exert strong conjugative stabilization of an adjacent carbon radical but can be considered as mildly activating on the basis of a comparison of the relative reactivities of these monomers and a series of common monomers toward a styryl radical.

The free radical polymerization of N, N-dimethylacrylamide

The free radical homopolymerization and copolymerization of N, N-dimethylacrylamide has been investigated at 50°C. Individual rate constants have been obtained for all the relevant propagation, transfer, and termination processes. The high propagation rate constant is due to the abnormal reactivity of the free radical rather than the monomer.

Free-radical polymerization and copolymerization of 2-butoxyethyl vinyl sulfide

1. It was shown that, in free-radical homopolymerization and copolymerization, 2-butoxyethyl vunyl sulfide is more reactive than vinyl ethers. 2. It was shown that 2,2′-azobis[2-methylpropionitrile] is a more reactive intiator in the reactions studied than benzoyl peroxide. In presence of the dinitrile, homopolymers of 2-butoxyethyl vinyl sulfide were prepared in yields of up to 65–68%, and its copolymers with methyl methacrylate were prepared in yields of up to 70–90%.