Kinetics of the anionic ring‐opening polymerization of octamethylcyclotetrasiloxane initiated by potassium isopropoxide

Kinetics of the anionic ring‐opening polymerization of octamethylcyclotetrasiloxane (D₄) in bulk initiated by potassium isopropoxide was studied. Several promoters including N‐methyl‐2‐pyrrolidinone (NMP), N,N‐dimethylformamide (DMF), and diglyme were used. It is indicated that the reactions are first‐order in D₄ during the initial stage of polymerization. The polymerization rate of D₄ is influenced by a number of factors, such as the nature of promoters, the molar ratio of promoter to initiator (C_p/C_i ratio), and the reaction temperatures. With the use of NMP as promoter, the polymerization rate constant at 30°C is 10.482 h^?1 with the C_p/C_i ratio equal to 3.0. As the C_p/C_i ratio increases, the polymerization rate constant increases sharply and the cyclic oligomers content in polymer decreases evidently. The back‐biting reaction that leads to the formation of decamethylcyclopentasiloxane (D₅) occurred in the polymerization of D₄. The rate of the D₅ formation relatively to the rate of D₄ conversion increases with the conversion of D₄. © 2006 Wiley Periodicals, Inc. J Appl Polym Sci 102: 3510–3516, 2006     

Semibatch anionic ring-opening polymerization of octamethylcyclotetrasiloxane in emulsion

The semibatch anionic ring-opening polymerization of octamethylcyclotetrasiloxane in emulsion was studied under the condition of no seed particles used in polymerization system. Concentration of emulsifier was set above critical micelle concentration. Effect of monomer feed rate on the chemical kinetics, average particle size and distribution and on the polymer molar mass and distribution was investigated. During monomer addition, polymerization rate was constant and controlled by the monomer feed rate. According to the proposed mechanism for anionic polymerization in emulsion, it was assumed that also the number of active polymerization sites and monomer concentration at the particle surface, where propagation occurs, remain constant. A continuous increase of average particle size and absence of extensive condensation reactions at high conversion suggested that the freshly added monomer diffuses toward hydrophobic polymer particles, where it is consumed in propagation reaction and/or accumulated in the particle core.     

Follow‐up of the course of the anionic ring‐opening polymerization of lactams onto an isocyanate‐bearing polymer backbone in the melt

In this study, a batch mixer was used as a rheoreactor to carry out and follow up in real time the rate of the anionic polymerization of ε‐caprolactam onto a 3‐isopropenyl‐α,α‐dimethylbenzene isocyanate bearing polypropylene (PP‐g‐TMI) in the presence of sodium ε‐caprolactam as a catalyst. The isocyanate group in the PP‐g‐TMI was capable of activating the anionic polymerization, leading to the formation of a graft copolymer with polypropylene as the backbone and polyamide 6 as the grafts. The polymerization rate was related to the viscosity increase of the polymerization system. The latter then resulted in a concomitant torque increase. It was shown that torque was a rapid, convenient, and approximate measure of the polymerization rate. The use of the torque allowed for rapid and approximate evaluation of the effects of chemical and operating conditions on the polymerization rate without the need to determine the monomer conversions. Torque profiles were also a very useful piece of information for the design of a reactive extrusion process for the same type of polymerization system. © 2006 Wiley Periodicals, Inc. J Appl Polym Sci 102: 4394–4403, 2006     

Anionic non‐equilibrium ring‐opening polymerization of octamethylcyclotetrasiloxane (D4) initiated by silazyl‐lithiums

The initiation and propagation reactions in anionic non‐equilibrium polymerization of octamethylcyclotetrasiloxane (D₄) initiated by silazyl‐lithiums are investigated. It is found that: both the steric hindrance effect and the electronic effect of the substitutes on the Si atom Si influences the initiation activity of silazyl‐lithiums; temperature effect on the propagation rate of D₄ increases strongly above 40 °C; the molecular weight distribution of the prepared polysiloxanes widens with time. © 2003 Society of Chemical Industry     

Reactive extrusion for the synthesis of nylon 12 and maleated low‐density polyethylene blends via the anionic ring‐opening polymerization of lauryllactam

Nylon 12 was successfully synthesized in a twin‐screw extruder via the anionic ring‐opening polymerization of lauryllactam (LL). Maleated low‐density polyethylene (LDPE–MAH) was added to improve the mechanical properties of nylon 12. The in situ blends of nylon 12 and LDPE–MAH were characterized by mechanical testing and scanning electron microscopy. With increasing LDPE–MAH content, the tensile strength and flexural strength decreased, whereas the blend had improved impact strength and achieved supertoughness when the content of LDPE–MAH was 30 wt %. In the in situ formed low‐density polyethylene‐g‐PA12 copolymer, the domain of the LDPE–MAH phase was finely dispersed in the nylon 12 matrix. The good interface between the two phases demonstrated that LDPE–MAH could be used as a macromolecular activator to induce the polymerization of LL. © 2009 Wiley Periodicals, Inc. J Appl Polym Sci, 2009     

Attapulgite@polymer particles with double‐layer polymer shell via soapless seeded emulsion polymerization

Attapulgite needle encapsulated with double‐layer polymer shell (ATP@DP) were prepared by the soapless seeded emulsion polymerization of the second monomer styrene in the dispersion of the attapulgite needle encapsulated with poly(methyl methacrylate) (ATP@PMMA), which was also conducted by the soapless seeded emulsion polymerization of the first monomer methyl methacrylate with the cetyltrimethylammonium bromide (CTAB) modified attapulgite needle (org‐ATP) as seeds. The different morphologies of ATP, ATP@PMMA particles, and ATP@DP particles were characterized by transmission electron microscopy, and the encapsulation mechanism was also discussed. © 2007 Wiley Periodicals, Inc. J Appl Polym Sci, 2008     

Characteristics of water-absorbent polymer emulsions

Water-in-Oil (W/O) and Oil-in-Water (O/W) type water absorbent polymer emulsions were studied using two different polymerization methods. W/O type water absorbent polymer emulsions were prepared by the inverse emulsion polymerization of ammonium acrylate (AA), the quaternized salt of dimethyl-aminoethyl methacrylate (DMQ) and acrylamide (AM) with N,N-methylene-bisacrylamide (MBA) as a crosslinker. A pH sensitive water absorbent polymer emulsion was prepared by the conventional emulsion polymerization of diethyl-aminoethyl methacrylate (DEAEMA) with ethylene glycol dimethacrylate (EGDMA) as a crosslinker. It was confirmed that the water absorption capacity of crosslinked polymers in inverse emulsion was controlled by crosslink density and dissociative charge density, and the crosslinked polyDEAEMA particles had a phase transition property of swelling and shrinking with pH. The dispersions of these water swollen crosslinked polymer particles exhibited an increase in viscosity and thixotropic fluidity.     

Influence of the chemical structure of transfer agents in coordinated anionic ring‐opening polymerization: application to one‐step functional oligomerization of ε‐caprolactone

Coordinated anionic ring‐opening polymerization of ε‐caprolactone in the presence of alcohols enables functional oligocaprolactones to be obtained easily in a single step. As observed by NMR and Maldi Tof mass spectroscopy, the functionalization of the oligomers, as well as the molecular weight distribution, depend strongly on the chemical structure of the alcohol. Hydroxy telechelic polymers can also be used as transfer agents. Finally, it was found that the chemical nature of the alcohol has a great influence on the kinetics, which suggests a coordination of this moiety on the Lewis site, during all the reaction. Copyright © 2004 Society of Chemical Industry     

Direct synthesis and characterization of crosslinked polysiloxanes via anionic ring‐opening copolymerization with octaisobutyl‐polyhedral oligomeric silsesquioxane and octamethylcyclotetrasiloxane

The crosslinked polysiloxanes were directly synthesized by anionic ring‐opening copolymerization of octaisobutyl‐polyhedral oligomeric silsesquioxane (POSS) as a multifunctional monomer with octamethylcyclotetrasiloxane (D₄) under base catalysts such as potassium hydroxide (KOH) or tetramethylammonium hydroxide (Me₄ NOH) siloxanolate. The mechanism of anionic ring‐opening copolymerization of octaisobutyl‐POSS and D₄ was discussed and the influences of the polar additive N,N‐dimethylacetamide on gelation time at different temperatures were investigated. The results of gel content and swelling ratio, GPC, solid‐state ²⁹Si and ¹³C NMR, FTIR, XRD show that octaisobutyl‐POSS is reacted and most of the product is crosslinked. The DSC and TG results indicate that the crosslinked polysiloxanes exhibit distinct glass transition temperatures (T_g) and excellent thermal stability. Compared to that under KOH siloxanolate, the crosslinked polysiloxane synthesized with Me₄NOH siloxanolate has better preferable thermal stability. © 2006 Wiley Periodicals, Inc. J Appl Polym Sci 102: 3848–3856, 2006     

High solids content emulsions. II. Preparation of seed latices

The preparation of concentrated seed latices for use in bimodal and trimodal formulations is presented in the current work. Various recipes of surfactant and initiator were tested in order to allow us to control the number of particles produced during the nucleation stage. Following this, a semi‐batch feed recipe that combined the use of oil‐soluble initiators and pre‐emulsified monomer was used to produce well‐defined latices having well defined particle size distributions. It was found that the primary concern in maintaining latex stability and favorable viscosity was the reduction of undesirable secondary nucleation. © 2002 Wiley Periodicals, Inc. J Appl Polym Sci 84: 1897–1915, 2002; DOI 10.1002/app.10512     

室温可自成膜中空微粒乳液的制备

采用羧基单体进行多阶段的种子乳液聚合,制备了内核为带羧基的聚合物、最外层为易成膜的低玻璃化温度聚合物、中间为轻度交联中间隔离层的多层核壳结构乳胶粒,最后通过碱处理制成了具有室温成膜性的中空结构聚合物微粒。研究表明,在反应前期以十二烷基苯磺酸钠为乳化剂,包壳阶段同时加入OP-10可有效控制乳胶粒结构形态,同时提高聚合物乳液的电解质稳定性;以甲基丙烯酸为羧基单体,其用量为核单体总量的30%(质量分数)时,聚合物微粒中空直径较大且微粒结构规整;碱处理温度以100℃为宜。在优化的工艺下,制得的室温可成膜中空聚合物微粒外径约500 nm,中空直径约300 nm。     

Preparation of titanium dioxide/poly(methyl methacrylate‐co‐n‐butyl acrylate‐co‐methacrylic acid) hybrid composite particles via emulsion polymerization

Titanium dioxide core and polymer shell composite poly(methyl methacrylate‐co‐n‐butyl acrylate‐co‐methacrylic acid) [P(MMA‐BA‐MAA)] particles were prepared by emulsion copolymerization. The stability of dispersions of TiO₂ particles in aqueous solution was investigated. The addition of an ionic surfactant, sodium lauryl sulfate, which can be absorbed strongly at the TiO₂/aqueous interface, increases the stability of the TiO₂ dispersion effectively by increasing the absolute value of the ζ potential of the TiO₂ particles. The adsorption of the nonionic surfactant, Triton X‐100, on the surface of TiO₂ particles is less than that of the ionic surfactant. Fourier transform IR spectroscopy was used to measure the content of MAA composite particles. Dynamic light scattering characterized the composite particle size and size distribution. The field‐emission scanning electron microscopy results for the composite particles showed a regular spherical shape, and no bare TiO₂ was detected on the entire surface of the samples. The composite particles that were produced showed good spectral reflectance compared to bare TiO₂. Thermogravimetric analysis results indicated the encapsulated TiO₂ and estimated density of composite particles. There was up to 78.9% encapsulated TiO₂ and the density ranged from 1.76 to 1.94 g/cm³. The estimated density of the composite particles is suitable at 1.73 g/cm³, which is due to density matching with the suspending fluid. The sedimentation experiment indicates that reducing the density mismatch between the composite particles and suspending fluid may enhance the stability. © 2005 Wiley Periodicals, Inc. J Appl Polym Sci 97: 72–79, 2005     

Preparation and characterization of titanium dioxide core/polymer shell hybrid composite particles prepared by emulsion polymerization

Titanium dioxide inorganic core and polymer shell composite poly(methyl methacrylate‐co‐butylacrylate‐co‐methacrylic acid) [P(MMA‐co‐BA)‐MAA] particles were prepared by emulsion copolymerization. Fourier transform IR (FTIR) spectroscopy was used to measure the content of MAA composite particles. Dynamic light scattering (DLS) characterized the composite particle size and size distribution. The field emission SEM (FE‐SEM) results of the composite particles showed regular spherical shape and no bare TiO₂ was detected on the whole surface of the samples. The composite particles were produced, showing good spectral reflectance compared with bare TiO₂. TGA results indicated the encapsulation efficiency and estimated density of composite particles. Encapsulation efficiency was up to 78.9% and the density ranged from 1.76 to 1.94 g/cm³. Estimated density of the composite particles is suitable to 1.73 g/cm³, due to density matching with suspending media. © 2004 Wiley Periodicals, Inc. J Appl Polym Sci 92: 2970–2975, 2004     

Morphology and thermal behavior of MCPA6/SAN blends prepared by anionic ring‐opening polymerization of ϵ‐caprolactam

In this article, a series of blends of monomer casting polyamide 6 and styrene‐co‐acrylonitrile (MCPA6/SAN) were prepared by in situ anionic ring‐opening polymerization of ?‐caprolactam. Their morphology and thermal behaviors were investigated by means of scanning electron microscope, differential scanning calorimeter, and wide‐angle X‐ray diffraction (WAXD), respectively. The SAN phase had much finer domain in MCPA6/SAN than that in the PA6/SAN blends prepared by melt blending of PA6 and SAN. All the melting and crystallization parameters of MCPA6/SAN blends decreased gradually with the increase of SAN content, while the melting temperature was almost unchanged. These results were due to the hydrolysis reaction of SAN that occurred during the anionic polymerization of ?‐caprolactam. In addition, WAXD results showed that only α crystal forms existed in the MCPA6/SAN blends. In addition, the mechanical property of MCPA6 was improved obviously by incorporating a certain amount of SAN. © 2006 Wiley Periodicals, Inc. J Appl Polym Sci 100: 1357–1363, 2006     

Zinc‐based catalyst for the ring‐opening polymerization of cyclic esters

A zinc‐based catalyst zinc bis[bis(trimethylsilyl)amide] was used for the polymerization of cyclic esters including L ‐lactide (L ‐LA) and 2‐methyl‐2‐carboxyl‐propylene carbonate (MBC). The polymerization of L ‐lactide in THF could be carried out successfully under mild conditions in very short time by using the zinc catalyst and alcohols as the initiators. Kinetic study in solution polymerization prooved the polymerization has high monomer conversion degree close to 100% and the molecular weight of the resulting polyester has linear increase with the increase of [M]₀ /[I] (molar ratio of monomer to initiator). Sequential polymerization of L ‐LA and MBC in THF also showed high MBC conversion of 94% with a narrow molecualr weight maintained, indicating a living nature of this polymerization. The zinc catalyst system has also been used for the L ‐LA bulk polymerization with a high monomer conversion. ¹³C NMR indicated the polymer possesses high regioregularity and the minor regioirregular component was owing to the D ‐LA in the monomer inserted into the polymer mainchain during the transesterifcation. Interaction between monomer and zinc catalyst has been found to be a key factor to sustain a homogenous solution during the initiating procedure. © 2011 Wiley Periodicals, Inc. J Appl Polym Sci, 2011     

New macromolecular silane coupling agents synthesized by living anionic polymerization; grafting of these polymers onto inorganic particles and metals

New macromolecular silane coupling agents, which are end-triethoxysilylated poly(styrene) and poly(tert-butylmethacrylate), were investigated as possible inorganic particle and metal surface treatment agents. These polymers containing poly(styrene) and poly(tert-butylmethacrylate) as the main chain, were prepared by living anionic polymerization. Grafting of the polymers onto inorganic particles and metals was performed via the hydrolysis of the triethoxysilyl group using either acidic or basic catalyst. n-Butylphosphate was used as the catalyst for grafting onto inorganic substances having an acidic surface such as silica. However, in the case of grafting onto inorganic substances having a basic surface, tetrabutylammoniumhydroxide was employed as the catalyst. Contrary to expectations, grafting onto titania was successful even in the absence of a catalyst. Particles grafted with these polymers showed excellent dispersibility in organic medium, in which the polymers are soluble. This phenomenon is in contrast to that for particles treated with polymers possessing triethoxysilyl groups at random positions of the chain or those treated with trimethylsilyl groups. Surface tension measurements of metal substrates coated with the grafted polymers, were found to be identical to the values obtained for the bulk polymers.     

Population balance modeling of particle size distribution in monomer‐starved semibatch emulsion polymerization

The evolution of particle size distribution (PSD) in the monomer‐starved semibatch emulsion polymerization of styrene with a neat monomer feed is investigated using a population balance model. The system under study ranges from conventional batch emulsion to semicontinuous (micro)emulsion polymerization depending on the rate of monomer addition. It is shown that, contrary to what is often believed, the broadness of PSD is not necessarily associated with the length of nucleation period. The PSDs at the end of nucleation are found to be independent of surfactant concentration. Simulation results indicate that at the completion of nucleation the particle size is reduced and the PSD narrows with decreasing rate of monomer addition despite nucleation time increasing. The broad distribution of particles frequently encountered in semibatch emulsion polymerizations is therefore attributed to stochastic broadening during the growth stage. The zero‐one‐two‐three model developed in this article allows perceiving that the dominant kinetic mechanism may be different for particles with different sizes. © 2009 American Institute of Chemical Engineers AIChE J, 2009     

Polystyrene latex particles bearing primary amine groups via soap‐free emulsion polymerization

Polystyrene latexes were prepared in the presence of an amino‐containing functional comonomer, N‐(3‐aminopropyl)methacrylamide hydrochloride (APMH), via soap‐free batch emulsion polymerization initiated by the cationic initiator 2,2′‐azobis(2‐amidinopropane) dihydrochloride. These latexes were characterized by studying the influence of the ionic comonomers on the polymerization kinetics, particle size, surface charge density and colloidal properties. The synthesized latexes were monodisperse with a final size between 100 and 600 nm depending on the APMH concentration. The initial polymerization rate and the particle number increased in accordance with the Smith–Ewart theory for soap‐free styrene emulsion polymerization with a hydrophilic functional comonomer. The final functionalization rate of the particles has been particularly studied with the intention of fitting the prepared latexes to be used in the immobilization of biological molecules for biological sample preparation and diagnostic applications. © 2020 Society of Chemical Industry     

Preparation of polydimethylsiloxane nanolatices by emulsion polymerization in a water–aminoethanol system

Stable and translucent polydimethylsiloxane nanolatices in a water–aminoethanol (AE) system were prepared by the emulsion polymerization of octamethylcyclotetrasiloxane (D₄) with nonionic polyoxyethylene alcohol ethers and polyoxyethylene aryl ether as surfactants and with KOH as an initiator. The effects of the AE concentration on the emulsion polymerization rate (R_p) of D₄ and the physical properties of the resultant nanolatices were investigated. Increasing the AE concentration in the reaction mixture dramatically increased the emulsion R_p value of D₄, and the kinetics of the D₄ emulsion polymerization in this system were consistent with the Morgan–Kaler theory of microemulsion polymerization. When the AE concentration in the emulsion increased, the transparency value of the resultant emulsion increased, and the size of the droplets in the resultant nanolatices decreased. In addition, the molecular weight of the polysiloxane in the resultant emulsion also increased with the increase in the AE concentration in the reaction mixture. A nanolatex prepared by the emulsion polymerization of 0.98M D₄ with 185 g/L AE had a transparency value of 80.9% and a mean diameter of 59.5 nm. The morphology of polysiloxane nanolatices cured with (N,N‐diethylaminomethyl)‐triethoxysilane was observed with transmission electron microscopy, and the size of the globular particles was consistent with that obtained by dynamic light scattering. © 2005 Wiley Periodicals, Inc. J Appl Polym Sci 98: 347–352, 2005     

Piloting of anionic polymerization of styrene in tetrahydrofurant

Anionic polymerization of styrene in THF with n‐butyllithium/alpha‐methylstyrene initiator is described as a first step in preparation of a styrenic block copoly‐mer. In order to suppress rapid decay of living alpha‐methylstyrene unimers, which occurred at room temperature, the initiation reaction was carried out at ?20(+5)°C. The kinetic parameters of this decay reaction were determined and used for process optimization. By combining experiments with modelling of styrene propagation reaction all key process parameters were defined for l‐L, 38‐L, and 189‐L reactors. A good match was demonstrated between the model and experimental propagation exotherm for semibatch reaction conditions. Overall, it was demonstrated that technical grade THF and styrene could be used at pilot plant scale to prepare well‐defined polymers up to Mn 22 000 via the “living” polymerization mechanism. The resulting polymers had narrow molecular weight distributions (1.06 < Mw/Mn < 1.30).