Experimental study of emulsion polymerization with crosslinking

Herein is reported the results of an extensive experimental investigation of the kinetics of emulsion polymerization as affected by crosslinking in the polymer particles. The model monomer system, methyl methacrylate (MMA) and ethylene glycol dimethacrylate (EGDMA), was chosen for this study due to its earlier comprehensive investigation in bulk polymerization. Standard recipes with sodium dodecylsulfate (SDS) as anionic emulsifier and potassium persulfate (KPS) as initiator were used for the batch emulsion polymerizations. Results, which clearly show the effect of crosslinking on the kinetics, are discussed in detail. These include swellability of polymer particles by monomer; polymer particle nucleation rates, below and above the critical micelle concentration (CMC); average number of radicals per particle; and gel-sol levels. It was found advantageous to use electron spin resonance (ESR) to follow radical concentrations during crosslinking in polymer particles. © 1997 John Wiley & Sons, Inc. J Appl Polym Sci 66: 935–957, 1997     

Thermal polymerization of styrene

An experimental investigation of the kinetics of bulk thermal polymerization of styrene in the temperature range of 200°–230°C is reported. Conversions and molecular weight averages were measured by gel permeation chromatography. At elevated temperatures, oxygen in the polymerization mixture appears to have negligible effect on the rate of polymerization and the molecular weights of the polymer. Experimental evidence suggests that the molecular weight development of the polymer is strongly influenced by transfer reactions.     

Optimizing nitroxide-mediated miniemulsion polymerization processes

Living/controlled radical polymerizations provide significant advantages in the control of polymer resin microstructure compared to conventional radical polymerization. Advances in our ability to tailor polymer microstructure will enable improvements in coatings properties and possible new applications of coating technologies. Adapting living radical polymerizations to heterogeneous media such as aqueous-based miniemulsion polymerization presents several challenges related to maintaining the livingness (the fraction of chains that are still “living” at the end of polymerization) of the polymer chains and also developing a commercially viable process. We have studied the nitroxide-mediated polymerization of styrene in miniemulsion, with the intent of maintaining a high degree of livingness by balancing the rates of biradical termination and disproportionation. We can now achieve >95% monomer conversion in less than three hours, while maintaining polydispersities ∼1.3. Monomer conversion can be dramatically increased from about 60–95% by changing the concentration of sodium dodecylbenzenesulfonate (SDBS) surfactant. Conversions in Dowfax 8390 stabilized miniemulsions showed no comparable dependency. Reasons for this potentially commercially important effect are under investigation.     

A kinetic investigation of butyl acrylate polymerization

An experimental investigation of the kinetics of the bulk free radical polymerization of butyl acrylate initiated with 2,2′-azobisisobutyronitrile (AIBN) was conducted at 50° and 60°C using two initiator concentrations. Conversion levels were measured by gravimetry and were independently confirmed using replicate runs. The experiments, conducted in glass ampoules, were performed over the full conversion range. A mathematical model for process simulation purposes was developed. The model was able to predict conversion at the two temperatures and initiator concentrations, thus providing a better understanding of the butyl acrylate homopolymerization kinetics.     

Free radical polymerization of p-methyl styrene

An experimental investigation is reported of the free-radical synthesis kinetics of poly(p-methyl styrene) in cyclohexane at low monomer conversion in the temperature range 50°–70°C using AIBN initiator. The p-methyl styrene monomer contained greater than 97% paraisomer. Isothermal conversion/time curves were obtained using glass ampoule reactors and gravimetry and molecular weight distribution and weight-average molecular weights were measured by s.e.c. and low angle laser light scattering photometry (LALLSP). Transfer to small molecules (monomer, cyclohexane, —) was found to be small or negligible with virtually all of the polymer chains formed by termination by combination. Predicted and measured weight-average molecular weights are in good agreement for polymer synthesized at low conversions.     

Synthesis and thermal polymerization of a novel stilbene-maleimide AB-monomer

Summary A novel AB-monomer, 3-maleimidostilbene (ST-MAI), was synthesized. DSC investigation indicated that the ST-MAI monomer melted at 127°C and thermally polymerized in the temperature range of 180 ∼ 300°C. IR investigation on the thermal polymerization processes proved that the thermal polymerization included not only copolymerizaiton between stilbene and maleimide, but also homopolymerization of maleimide. The largest reaction conversion of maleimide and stilbene unit in a ST-MAI monomer was about 82% and 50% respectively. The glass transition temperature of cured ST-MAI resin was 234°C, determined by DSC. The decomposition temperatures for 10% weight loss was above 430°C in both air and nitrogen atmospheres. Received: 14 July 1999/Revised version: 30 September 1999/Accepted: 5 October 1999     

Analysis of tanks-in-series model with backflow for free-radical polymerization

Free-radical polymerization in a flow reactor represented by the tanks-in-series model with backflow was considered. Conversions and molecular weight distributions were computed as functions of the backflow parameter, and the results were compared with the conversion and molecular weight distribution from a CSTR and those from a plug-flow reactor. Backflow was found to be undesirable for the polymerization mechanism under investigation. Values of the degree of segregation for the tanks-in-series model were calculated by using Zwietering's approach as a function of backflow.     

New peracid-type polymeric initiator for radical polymerization

In this study, a radiation-induced copolymer, namely polyethylene-g-acrylic acid powder, was used, whose carboxyl groups can be oxidized to form a highly reactive polymer initiator. The activation energy for its decomposition is 22.4 kcal/mol. It was found that the peracid-type polymeric powder was effective as an initiator for radical polymerization. It had high reactivity toward 2-hydroxyethyl methacrylate (HEMA), which could be easily grafted onto the polymeric powder; also, the homopolymer could be obtained. The kinetic investigation indicated that this polymerization proceeded by a radial mechanism, and the overall activation energy of homopolymerization was 18.67 kcal/mol and the overall activation energy of bigraft polymerization was 17.35 kcal/mol. By using the peracid-type polymeric powder as initiator for the copolymerization of methyl methacrylate with styrene, it was confirmed that the polymerization initiated by the peracid-type polymeric powder was a radical reaction.     

Versatile laboratory‐scale polymerization reactor system

A novel lab‐scale reactor system designed for investigation of olefin polymerization reactions using homo‐ and heterogeneous catalysts is introduced. The high inert atmosphere level of the system is based on stainless‐steel lines and cylinders, a nitrogen/vacuum technique, and removable reactants chambers which are packed in a glove‐box. The solvent is transferred straight from the distiller through the reagents' containers into the reactor. The reactor is equipped with an ethylene pressure/mass flow and two temperature‐control systems. Data acquisition is based on a personal computer and software for monitoring and data storage. The results of versatile ethylene copolymerization with cyclopentene, cyclooctene, and cyclododecene with this reactor system are discussed. © 2000 John Wiley & Sons, Inc. J Appl Polym Sci 77: 2921–2928, 2000     

Bulk polymerization of acrylonitrile. I. An experimental investigation of the kinetics of the bulk polymerization of acrylonitrile

A comprehensive experimental investigation is reported of the bulk polymerization of acrylonitrile (AN) to limiting conversion using 2,2′-azobisisobutyronitrile (AIBN) as initiator at 40°, 60°, and 80°C. Molecular weight development was followed by gel permeation chromatography (GPC).     

Synthesis of a new oxazoline macromonomer for dispersion polymerization

We synthesized new macromonomers containing vinylsilane moiety by cationic ring-opening polymerization of 2-ethyl-2-oxazoline. Kinetic studies proved that initiation with vinylsilane derivative, bearing chloride counterion, is a fast process followed by a slow propagation and absence of termination. We used the dispersion polymerization of styrene as test for the stabilizing efficiency of the newly synthesized macromonomer. The dispersion polymerization tests allowed the investigation of the effect of the macromonomer concentration on the number average diameter of the prepared polystyrene microspheres and its polydispersity index. In addition, we compared the stabilizing efficiency of commercial poly(N-vinylpyrollidone) with that of our macromonomer. Copolymerization of styrene with 10 wt% oxazoline macromonomer yielded stable and monodisperse microspheres, having the number average diameter of 1.8 μm and a good size polydispersity index of 1.05.     

Experimental investigation on high conversion free-radical polymerization of behenyl acrylate

An experimental investigation on the kinetics of free-radical polymerization of behenyl (a mixture of 14.8% n-octadecyl, 15.1% n-docosyl) acrylate initiated with benzoyl peroxide was conducted at 70°C using a HAAKE rotational viscometer. Molecular weight measurements and differential scanning calorimetric studies of the samples are also described and the results are compared with those obtained by batch reactions conducted under a nitrogen atmosphere. A high monomer order of 1.61±0.11 and a low initiator order of 0.35±0.04 was obtained. The role played by the long methylene chain in behenyl acrylate is also discussed. © 1994 John Wiley & Sons, Inc.     

Approaches to branched polystyrene using bulk free-radical polymerization

Preparation of branched polystyrene using continuous bulk styrene polymerization is extremely difficult due to gel formation and can even lead to reactor plugging. This investigation explores the concept of post-polymerizer branching by placing latent functional groups along the polymer backbone which couple during high-temperature devolatilization of the polymerized effluent. The latent functional monomer pair investigated is glycidyl methacrylate and acrylic acid. The key to producing a branched polystyrene that is thermally stable is to add one of the latent functional monomers in large excess, making the other monomer the limiting reagent. © 1997 John Wiley & Sons, Inc. J Appl Polym Sci 64: 683–687, 1997     

Kinetics and reaction mechanism of template polymerization investigated by conductimetric measurements. 2. Radical polymerization of sodium methacrylate in the presence of poly(allylamine) hydrochloride

The polymerization of sodium methacrylate in water was investigated using conductimetry and dilatometry. Conductimetry was shown to be a reliable tool for the determination of the kinetic parameters of the blank polymerization (order of reaction with respect to monomer and initiator, activation energy). The conductimetric investigation of template polymerization of the acrylic monomer onto poly(allylamine) hydrochloride at low monomer concentration indicates that the reaction proceeds by a ‘zip’ mechanism. © 1999 Society of Chemical Industry     

Stereoselectivity of the ring-opening polymerization of cyclo-octadiene-1,5

Stereoselectivity of the ring-opening polymerization of cyclo-octadiene-1,5 (COD) in the presence of WCI₆-[(i-C₄H₉₂Al]₂O has been studied. It has been shown that with COD just as in the case of cyclooctene (CO) and bicyclo [6.1.0] nonene-4 (BCN) studied previously, the polymer microstructure is determined by two factors: ‘the stereoselectivity of an elementary act of cyclo-olefin ring-opening’ and secondary isomerization reactions of a polymer chain. The ¹³C n.m.r. study shows that variation in the microstructure with conversion is accounted for by isomerization of a polymer chain. Arguments supporting the hypothesis of the formation of two types of units at the same active site are discussed, based on results of investigation of sequences of cis-and trans units in the polymer chain and the temperature dependence of stereoselectivity of an elementary act of ring-opening with COD, CO and BCN.     

Preparation and polymerization of isopimaric acid derivatives

Isopimaric acid is a typical rosin compound and can account for 30% of the total mass of slash pine rosin. The molecular structure of isopimaric acid derivatives features an unsaturated double bond at the C13 position, opening up the possibility of their industrial polymerization. In this study, isopimaric acid (95.4%), methyl isopimarate (99.5%), and allyl isopimarate (95.1%) were prepared as highly pure monomers. New experimental results are presented and mechanisms based on the investigation of free-radical polymerization under UV irradiation are proposed. New rosin monomers for potential value-added utilization of woody biomass are also identified. © 2019 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2019 , 136, 47817.     

Bulk polymerization and characterization of isocyanatoacrylate copolymers

The purpose of this investigation was to prepare by bulk polymerization six new isocyanatoacrylate copolymers and to characterize them. The isocyanatoacrylate copolymers, which were prepared by tri‐n‐butylborane oxide (TBBO)‐initiated free‐radical polymerization, were formed from 1 : 1 mol mixtures of 2‐isocyanatoethyl methacrylate (IEM) with 2‐hydroxyethyl methacrylate (HEMA), hydroxypropyl methacrylate (HPMA), 2‐hydroxyethyl thiomethacrylate (HETMA), ethylthioethyl methacrylate (ETEMA), 2‐(acetoxyacetoxy)ethyl methacrylate (AAEMA), and tetrahydrofurfuryl methacrylate (THFMA). These six copolymers were compared to the homopolymer of IEM, which was polymerized in an identical fashion. The bulk polymers were fractionated into their acetone‐soluble and acetone‐insoluble components. Physical characterization via photoacoustic infrared (PASIR) spectroscopy showed vast differences in residual isocyanate content. Differential scanning calorimetry (DSC) thermal analysis was carried out on all polymers. Elemental analysis (nitrogen) determined the ratio of IEM to the comonomer and boron analysis showed whether the initiator stayed in the acetone‐insoluble fraction or was “extracted” into the acetone‐soluble fraction. In conclusion, we found that the composition of the copolymers correlated well with the predicted design. © 1999 John Wiley & Sons, Inc. J Appl Polym Sci 74: 1577–1583, 1999     

A kinetic study of crosslinking vinyl polymerization by laser Raman spectroscopy

Summary Kinetic studies of crosslinking vinyl polymerizations are usually only applicable to the initial stages of the reaction, prior to the gel point, due to the subsequent insolubility of the polymer and the great increase in viscosity. We have demonstrated the suitability of laser Raman spectroscopy for quantitative analysis over the entire conversion range in an investigation of the polymerization of diethylene glycol bis (allyl carbonate) in bulk, with benzoyl peroxide initiation, between 70 and 85°C. The rate of consumption of vinyl bonds could be approximated by first-order kinetics up to ca. 80% depletion. Lower rates were observed at higher conversions.     

On the possibility of using combined polymerization and drying in synthesis of polyacrylamide

This paper presents investigation results of polyacrylamide synthesis with combined polymerization and drying. First, polyacrylamide synthesis was carried out in concentrated aqueous solutions of acrylamide at 30°C. Polymerization was initiated by K₂S₂O₈/Na₂S₂O₃ an oxidation–reduction system. The monomer conversion degree at this stage did not exceed 80%. Further, polymerization with simultaneous solvent elimination from the prepolymer was carried out in a dryer with infrared heat supply and natural convection. Such conditions provide monomer conversion degree up to 100%.