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The synthesis of a new copolymer poly(α-methylstyrene-block-isobutyl vinyl ether) by cationic polymerization is reported. The polymerization was performed in bulk under suitable condition at temperature 0 °C. The copolymer was prepared by the reaction of alpha-methylstyrene (α-MS) with isobutyl vinyl ether (IBVE), in the presence of a natural Algerian montmorillonite clay modified by 0.05–1 M H2SO4, known as Maghnite-H+, as proton source, a non-toxic and an efficient catalyst for cationic polymerization of many vinylic and hetero-cyclic monomers. It was found that H2SO4 concentration allows controlling the chemical composition, the porous structure of the acid-activated clays, and their catalytic performance. The maximal yield of polymer is observed in the presence of Algerian MMT modified by 0.25 M H2SO4. Effects of α-MS/IBVE molar ratio, catalyst concentration, on yield and molecular weight of polymer were revealed in the presence of the most active sample. The structure of the products obtained is confirmed by 1H-NMR, 13C-NMR (nuclear magnetic resonance), Fourier transform infrared spectroscopy, differential scanning calorimetry, and gel-permeation chromatography, finally, a mechanism for the reaction was proposed.

Hollow poly(alpha-methylstyrene) (PAMS) shows application in inertial confinement fusion experiments as the degradable mandrels of glow plasma polymer shells. However, the molecular weight of PAMS has great influence on the quality of mandrels. In this work, this influence was systematically studied using several PAMS samples with different molecular weights. For PAMS shells with 900 μm inner diameter and different wall thickness, when the molecular weight of PAMS is in the range of 300–500 kg·mol−1, perfect sphericity and good wall thickness uniformity can be obtained. In contrast, when increasing molecular weight to 800 kg·mol−1, the sphericity and the wall thickness uniformity become worse. Moreover, compared with the wall uniformity, the sphericity of PAMS shells was much less sensitive to the molecular weight. The results also showed that the stability of W1/O compound droplets of PAMS shells were less affected by the molecular weight. It was revealed that the wall uniformity and the sphericity of the PAMS shells were associated with the diffusion rates of fluorobenzene (FB). Keywords: Poly(alpha-methylstyrene), Molecular weight, Sphericity, Wall thickness uniformity, Diffusion rate, PACS Codes: 52.57.Bc, 47.85.md

The aim of this study was to develop the efficient and versatile method for the synthesis of block copolymers consists by cationic polymerization vinylidene chloride (VDC) and alpha-methylstyrene (alpha-MS) in the presence of a natural Algerian montmorillonite clay modified by 0.05–0.35 M H2SO4 (Algerian MMT-H+). It was found that H2SO4 concentration allows controlling the chemical composition, the porous structure of the acid-activated clays and their catalytic performance. The maximal yield of polymer is observed in the presence of Algerian MMT modified by 0.25 M H2SO4. Effects of VDC/MS molar ration, catalyst concentration, reaction time, reaction temperature and polarity medium on yield and molecular weight of polymer were revealed in the presence of the most active sample.

Phase equilibria of 3-methylstyrene, 4-methylstyrene, alpha-methylstyrene and a methylstyrene mixture (mainly 3-methylstyrene (60% mol) and 4-methylstyrene (40% mol)) in supercritical CO 2 were measured using high-pressure variable-volume view cells based on the static synthetic method. The systems were investigated between 308 and 353 K, with mass fractions of solute ranging continuously from 0.0275 to 0.65 and pressures up to 15 MPa. The experimental data shows a linear relationship between the phase transition pressure and the system temperature at constant composition. When the solubilities are compared, the methylstyrene isomers show little yet significant differences between them with the methylstyrene mixture being the most soluble. As the temperature increases, a decrease in the difference between the phase transition pressures of the methylstyrene structural isomers were observed. Lastly, the experimental data were correlated with the Peng-Robinson cubic equation of state using one temperature-independent binary interaction parameter and satisfactory results were obtained in both low and high solute concentration regions.

The kinetics of the free radical terpolymer system methyl methacrylate (MMA)/alpha methyl styrene (AMS)/butyl acrylate (BA) have been studied in detail. Previous work with terpolymer systems typically has not involved monomers or cases where depropagation was a significant concern and hence the Alfrey–Goldfinger model was adequate to describe the system. In other works involving the MMA/AMS/BA system, modelling of the kinetics has not been attempted. In order to properly study this system, a new model has been developed based upon some of the underlying principles of the binary Kruger model (Kruger et al., 1987. Ein modell zur beschreibung reversibler copolymerisationen. Makromolecular Chemie, 188, 2163–2175.). A sensitivity analysis and benchmarking of the new model has been done and the terpolymerization system has been studied at 140 ∘ C for selective feed ratios with promising results.

資料番号: AA0047900001

Space charge is formed in cables insulated with crosslinked polyethylene. It has not been clear whether the crosslinking byproducts or the crosslinked polymer morphology is responsible for the space charge formation. In order to clarify this point additive-free noncrosslinked low-density polyethylene, additive-free crosslinked polyethylene, and degassed crosslinked polyethylene were soaked in the crosslinking byproducts and the space charge distribution was measured after DC voltage application. Samples tested are divided into two categories. The first category is a soaked single-layered sheet and the second category is a two-layered specimen consisting of a soaked sheet and a nonsoaked sheet. As a result, the following conclusions were obtained. (1) Cumyl alcohol is responsible for homocharge layers in front of the electrodes in both low-density and crosslinked polyethylene sheets. (2) Acetophenone is responsible for heterocharge formation in crosslinked polyethylene, presumably as a synergistic effect with water. (3) alpha -methylstyrene has no effect on space charge formation in low-density polyethylene, while it assists charge trapping in crosslinked polyethylene. (4) Charge trapping occurs easier in degassed crosslinked polyethylene than in low-density polyethylene, probably because of carbonyl groups induced by crosslinking

The spin–lattice relaxation time T1 and nuclear Overhauser enhancement NOE were determined for three samples of atactic oligo- and poly(α-methylstyrene)s (a-PαMS) with weight-average degree of polymerization xw = 2, 3, and 67.1 in cyclohexane at 30 °C. A comparison is made of the present data for T1 and NOE with the helical wormlike (HW) chain theory, and it is shown that the theory may explain well the data for large xw (≳ 10). For smaller xw, the rigid sphere model having the radius equal to the apparent root-mean-square radius of gyration of the HW chain fails to give a quantitative explanation of T1 in contrast to the case of the relaxation time τΓ determined from dynamic depolarized light scattering measurements, indicating that the nuclear magnetic relaxation and dynamic depolarized light scattering cannot be described in terms of a common single relaxation time. However, it is shown that there is an effective (mean) magnetic relaxation time τM approximately equal to 0.6τΓ. From a comparison of the present results for T1 for a-PαMS with previous ones for typical flexible polymers, it is also shown that the behavior of T1 for them, including a-PαMS, may be consistently explained by the use of τM (proportional to τΓ).

Dynamic Depolarized Light Scattering by Oligo- and Poly(α-methylstyrene)s in Dilute Solution

Alpha-methylstyrene (AMS) can be effectively dimerized by a free-radical mechanism mediated by the catalytic chain transfer (CCT). Above the ceiling temperature of AMS, 61 °C, the dimer may become almost an exclusive product with only a small percentage of impurity of AMS trimer and tetramer. Kinetics of the AMS oligomerization has two characteristic features. First, the rate of the oligomerization increases with concentration of the CCT catalyst. Second, conversion reaches a plateau at 60–70%. A kinetic scheme explained both effects. Besides AMS, para- and methasubstituted AMS can also be dimerized. Orthosubstituted AMS's do not oligomerize. © 2002 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 40: 1366–1376, 2002

Rieselbettreaktoren finden in der chemischen Industrie breite Anwendung zur Realisierung heterogen-katalysierter Reaktionen insbesondere bei hohen Eduktdurchsätzen. Allerding ist die Reaktorleistung durch geringe Stoff- und Wärmeübertragungsraten begrenzt. Zusätzlich können sich Fehlverteilungen der Flüssigphase nachteilig auf Transportprozesse, Katalysatorausnutzungsgrad und -aktivität auswirken. Konzepte mit dynamischer Betriebsweise, wie beispielsweise die periodische Variation des Flüssigphasendurchsatzes am Reaktoreingang, wurden vorgeschlagen, bei denen die zeitgemittelten Raum-Zeit-Ausbeuten gesteigert werden konnten. Dispersionsvorgänge schwächen die positiven Effekte jedoch mit zunehmender Länge des Festbetts ab. Ein alternatives quasi-periodisches Reaktorkonzept ist der geneigt rotierende Festbettreaktor, bei dem die zeitliche in eine örtliche periodische Betriebsweise überführt wird. Die Reaktorneigung führt zur Separation der Gas- und Flüssigphase; die überlagerte Reaktorrotation resultiert in einer periodischen Be- und Entnetzung der im Reaktor fixierten Katalysatorschüttung, wodurch die Zugänglichkeit der aktiven Zentren für die Edukte, insbesondere der Gasphase, über die gesamte Reaktorlänge verbessert wird. Beim neuen Reaktorkonzept können sowohl die Drehzahl als auch die Neigung in Abhängigkeit vom Reaktionssystem (Reaktionsrate, Flüssigkeitseigenschaften, Katalysator etc.) angepasst werden, um die Strömung (siehe Abbildung 1) für den jeweiligen Prozess zu optimieren. Zur Leistungsbewertung des neuen Reaktorkonzepts wurde zusätzlich zur hydrodynamischen Charakterisierung die jeweilige Strömung hinsichtlich der Raum-Zeit-Ausbeute einer Modellreaktion vergleichend zum Rieselbettreaktor untersucht. Als Modellreaktion wurde die irreversible unselektive Hydrierung von α-Methystyrol zu Cumol (C9H10+H2 --> C9H12) verwendet, bei der bereits bei moderaten Prozessbedingungen Stoffübertragungs¬limitierungen der Gasphase auftreten (Khadilkar et al., 1999). Die Veränderungen beim Reaktionsumsatz in Abhängigkeit von den Betriebsbedingungen (p = 1 bar und 6 bar, T = 25 °C und 40 °C, isotherm) können damit direkt der Stoffübertragung zugeordnet werden. Für die reaktionstechnischen Studien wurde der Reaktor mit einer dünnen Schicht Palladium-Katalysator (kugelförmiges γ-Al2O3-Trägermaterial, Ø 4 mm, egg-shell, 0,1 Ma.-% Pd) in der Mittelebene des Reaktors (L = 1,6 m, D = 0,1 m) zwischen Inertmaterial befüllt.

Nuclear magnetic resonance spectroscopy (NMR) in solution and solid state was applied to obtain response of the chemical behaviour of commercial poly(alpha–methylstyrene) (PAMS). From solution measurements it was possible to determine the microstructure of this amorphous homopolymer. The solid state NMR investigation showed that the CPMAS 13 C routine spectrum allowed us to obtain information on the polymer microstructure and also evaluate the domain mobilities. The variation contact time and the proton spin-lattice relaxation time were determinant factors to evaluate the dynamic molecular motion.

A series of novel polyarylethersulfone (AB)(n) block copolymers with different segment lengths have been synthesized by nucleophilic solution polycondensation of phenoxide-terminated and fluorine-terminated oligomers; random copolymers have been prepared over the whole composition ranges. The structures of the resultant copolymers have been confirmed by FTIR, C-13 NMR spectra and differential scanning calorimetry (DSC). Compared with two homopolymers and random copolymers, the block copolymers of this study possess excellent thermal stability (5% thermal decomposition under nitrogen atmosphere above 500 C) and high glass transition temperatures, and have a wide melt-processing temperature range. They may become a new class of mouldable high performance thermoplastics. (C) 2001 Society of Chemical Industry.

Mixtures of Poly (metyl methacrylate) (PMMA) and poly (α-methylstyrene-co-acrilonitrile) (αMSAN) exhibit a LCST type of phase behavior. Dynamic rheological properties of PMMA/αMSAN blends of various compositions were measured at temperatures below, near, and above the phase-separation temperature. The time-temperature superposition was tried to obtain the master curves of G' and G" at 160°C. The time-temperature superposition principle failed above a certain temperature due to a phase separation. The “breakdown” temperature is close to the cloud temperature Tc of the blend samples. Comparison of logG' vs. logG" relation between the two components and the blends was made. The results show that the slopes of logG' vs. logG" plots in the terminal region are dependent on the composition of the blends. The rheological measurements have been found to be useful for characterizing the phase-separation of PMMA/αMSAN blends.

A new model for synthesis of the plastics, block copolymers were prepared from methyl methacrylate (MMA) and alpha-methyl styrene (α-MS) by cationic copolymerization in the presence of a new and efficient catalyst of “Maghnite-Na” at 0 °C in bulk. In this paper, the copolymerization of α-MS and MMA was induced in heterogeneous phase catalyzed by Maghnite-Na was investigated under suitable conditions. The “Maghnite-Na” is a montmorillonite sheet silicate clay, with exchanged sodium cations to produce Na-Montmorillonite (Na+-MMT) obtained from Tlemcen, Algeria, was investigated to remove heavy metal ion from wastewater as an efficient catalyst for cationic polymerization of many vinylic and heterocyclic monomers. The synthesized copolymer were characterized by Nuclear Magnetic Resonance (NMR-1H, NMR-13C), FT-IR spectroscopy, Differential Scanning Calorimetry (DSC), and Gel Permeation Chromatography (GPC) to elucidate structural characteristics and thermal properties of the resulting copolymers. The structure compositions of “MMT”, “H+-MMT” and “Na+-MMT” have been developed. The effect of the MMA/α-MS molar ratio on the rate of copolymerization, the amount of catalyst, temperature and time of copolymerization on yield of copolymers was studied. The yield of copolymerization depends on the amount of Na+-MMT used and the reaction time. The kinetic studies indicated that the polymerization rate is first order with respect to monomer concentration. A possible mechanism of this cationic polymerization is discussed based on the results of the 1H-NMR Spectroscopic analysis of these model reactions. A cationic mechanism for the reaction studies showed that monomer was inserted into the growing chains. Copyright © 2016 BCREC GROUP. All rights reservedReceived: 2nd May 2015; Revised: 24th February 2016; Accepted: 15th March 2016How to Cite: Ayat, M., Belbachir, M., Rahmouni, A. (2016). Methyl Methacrylate and Alpha-Methyl Styrene: New Strategy for Synthesis of Bloc Copolymers for Use in Potential Biomedical Applications Generated by an Ecologic Catalyst called Maghnite (Algerian MMT). Bulletin of Chemical Reaction Engineering & Catalysis, 11 (3): 316-329 (doi: 10.9767/bcrec.11.3.571.316-329)Permalink/DOI: http://doi.org/10.9767/bcrec.11.3.571.316-329

α-Methylenebenzocyclobutene (MB) was prepared by Wittig reaction of 1-(triphenylphosphonio)benzocyclobutene bromide with paraformaldehyde in 70% yield. Radical polymerization of MB afforded poly(α-methylenebenzocyclobutene) (PMB) in 66% yield (M n = 20 000). MB, which can be regarded as a cyclic analog of α-methylstyrene, had a higher polymerizability than α-methylstyrene. The higher polymerizability of MB was confirmed by semiempirical molecular orbital calculation by comparison with that of α-methyleneindane. Radical copolymerizations of MB with styrene (St), methyl methacrylate (MMA), and maleic anhydride (MANH) gave corresponding copolymers quantitatively. Especially, the copolymerization with MANH afforded the corresponding alternating copolymer. Q and e values of MB were determined as 1.35 and -1.00, respectively, from the results of the copolymerizations with MMA. Thermal properties of the obtained PMB were examined, and the thermal decomposition of PMB was discussed.

The first efficient synthesis of poly(α-methylstyrene-b-isobutylene-b-α-methylstyrene) (PαMeSt-PIB-PαMeSt) triblock copolymer thermoplastic elastomers (TPEs) has been accomplished by living cationic polymerization using sequential monomer additions. Living PIB was prepared by the 5-tert-butyl-1,3-bis(1-chloro-1-methylethyl)benzene (tBuDicumcl)/TiclJHex :Mecl 60 :40 v :v/-80°C polymerization system. The living ends were capped by 1,1-diphenylethylene (DPE). TiCl 4 was replaced by SnBr 4 , followed by the addition of αMeSt. Triblock copolymers with close to theoretical molecular weights and narrow molecular weight distributions (M w /M n ∼1.1) were obtained. Homopolymer and diblock contamination have been found to be negligible. The thermal stability of the triblock copolymer was characterized by thermogravimetric analysis. Microphase separation was evidenced by the two glass transitions (at -65 and +180°C) observed by differential scanning calorimetry and in dynamic mechanical analysis. Triblock morphology was examined by transmission electron microscopy. Compression-molded samples with 16-45 wt % PαMeSt exhibited 12-24.5 MPa tensile strength, apparently directly related to the PαMeSt content and independent of the PIB molecular weight.

Linear styrene-butadiene block copolymers of the polyA-block-polyB-block-polyA type (SBS) have been synthesized using a dicarbanion initiator formed by the reaction of metal lithium and α-methylstyrene. While being unable to initiate polymerization in cyclohexane and/or n-hexane, the diinitiator performed well in benzene. Various promoters such as tetrahydrofuran (THF), tetramethylethylenediamine, and hexamethylphosphoric triamide have been added during the making of diinitiators, resulting in initiators of different functionalities and activities. The presence of THF facilitated the formation of the diinitiator, and the resulting polymers made with this diinitiator have been analyzed and mechanically tested. The effect of process variables on the polymerization kinetics and molecular characteristics was also investigated.

The polymerization of α-methylstyrene (αMeSt) was investigated using the 2-chloro-2,4,4-trimethylpentane (TMPClTiCl 4 /methyl chloride :hexane (40 :60, v :v)/-80 °C system as a model to determine the efficiency of crossover from living polyisobutylene (PIB) to αMeSt. Low initiator efficiencies and broad molecular weight distributions were obtained. Living polymerization of αMeSt was achieved by first converting TMPCl to the corresponding diphenylalkylcarbenium ion by capping with 1,1-diphenylethylene (DPE), followed by the addition of titanium(IV) alkoxide to decrease the Lewis acidity. The initiator efficiencies, however, were lower than 100%. Living polymerization with ∼100% initiator efficiency was achieved by SnBr 4 as coinitiator. First, TMPCl is transformed to the corresponding diphenylalkylcarbenium ion by capping with 1,1-diphenylethylene. Subsequently, titanium(IV) isopropoxide is introduced to deactivate TiCl 4 , followed by the addition SnBr 4 and αMeSt. The success of the method was demonstrated by the synthesis of PIB-poly(α-methylstyrene) diblock copolymers without homopolymer contaminants.

We describe the use of poly(alpha-methylstyrene peroxide) (P alpha MSP), an alternating copolymer of alpha-methylstyrene and oxygen, as initiator for the radical polymerization of vinyl monomers. Thermal decomposition of P alpha MSP in 1,4-dioxane follows first-order kinetics with an activation energy (E(a)) of 34.6 kcal/mol. Polymerization of methyl methacrylate (MMA) and styrene using P alpha MSP as an initiator was carried out in the temperature range 60-90 degrees C. The kinetic order with respect to the initiator and the monomer was close to 0.5 and 1.0, respectively, for both monomers. The E(a) for the polymerization was 20.6 and 22.9 kcal/mol for MMA and styrene, respectively. The efficiency of P alpha MSP was found to be in the range 0.02-0.04. The low efficiency of P alpha MSP was explained in terms of the unimolecular decomposition of the alkoxy radicals which competes with primary radical initiation. The presence of peroxy segments in the main chain of PMMA and polystyrene was confirmed from spectroscopic and DSC studies. R(i)'/2I values for P alpha MSP compared to that of BPO at 80 degrees C indicate that P alpha MSP can be used as an effective high-temperature initiator.

SANS measurements are presented for the system living poly(α-methylstyrene) in deuterated THF, using sodium naphthalide as the initiator. We study three samples, differing in the ratio, r, of the number of moles of initiator to the number of moles of initial monomer and differing in the mole fraction of initial monomer. We compare the data to a theory for the scattering which treats the polymerization as a phase transition in the mean field approximation and also to a theory based on the dilute n→0 magnet model (where n is the dimension of the order parameter) in which no mean field assumption is made but in which an assumption of no solvent interaction is made

LDPE films were soaked into crosslinking byproducts which are acetophenone, a-methylstyrene and cumyl alcohol. The samples were used to perform the breakdown test. The ac breakdown measurements were conducted at a ramp rate of 50V/s at room temperature. Weibull plot is used to analyze the ac breakdown result. Comparing the soaked and un-soaked samples, it does show a small change in the characteristic breakdown strength as the LDPE film were soaked into the sample depending on the byproducts. It suggests that the breakdown strength is modified by adding the byproducts in the LDPE film. However, as the range of breakdown strength of all samples are to be compared, these values fall in the same region which indicate no significant difference can be seen in the samples. AC Pulsed Electroacoustic (PEA) technique was used to measure space charge in the samples. The result obtained from this test is used to explain the breakdown phenomena in the crosslinking byproduct soaked LDPE and space charge characteristics.

Novel telechelic poly(methyl methacrylate) having OH and COOH groups in the chain was prepared by anionic polymerization with the difunctional initiator made by the reaction betweem 4-[2-(tert-butyldimethylsiloxy)ethyl]-α-methylstyrene and sodium napththalene, followed by termination with CO 2 and hydrolysis of the tert-butyldimethylsiloxy group. OH groups were introduced quantitatively, but the number of the terminal COOH groups per molecule was 1.7±0.1 which is less than the theoretical value, 2

Surface morphology and compositions of multiblock and starblock copolymers of poly(a-methyl styrene) (PMS) and poly(dimethyl siloxane) (PDMS) were investigated by cross-sectional transmission electron microscopy, angle- and energy-dependent ESCA, and infrared spectroscopy. The extent of surface segregation of PDMS was determined for multiblock and starblock copolymers to depth of 210{angstrom}. No surface excess was with high PDMS bulk concentrations (60 wt%) have a highly oriented lamellar morphology in the near air surface region, and the topmost air surface region (27 {angstrom}) is exclusively composed of PDMS. The PMS-PDMS block copolymers with lower PDMS bulk concentrations (40 wt%) have lesser or no domain orientation and the surface region includes detectable PMS.

Absolute configuration assignments of poly(methyl methacrylate) (PMMA) and poly(α-methylstyrene) (PAMS) are derived from proton-detected heteronuclear shift-correlated NMR spectra. When recorded with high digital resolution, spectra display characteristic skewed coupling patterns caused by passive geminal methylene coupling in tetrads that lack a center of symmetry. It is shown how this information can be used for interpreting NMR spectra of vinyl polymers. A partial hexad interpretation of the methylene 13 C spectrum of PMMA is given

Poly(alpha-methylstyrene) with narrow molecular weight distribution (MWD) was obtained by cationic polymerization initiated by iodine in CH 2 Cl 2 /liquid SO 2 (80/20 vol.%) or tuluene/liquid SO 2 (45/55 vol.%) mixed solvent at -60°C. The average number molecular weights of the product polymers increased with monomer conversion but the dependence was not linear because of the low initiation efficiency at the beginning of the reaction. On addition of a fresh feed of monomer at the end of polymerization, the added feed was polymerized at the same rate with an increase of molecular weight.

The formation of space charge in Crosslinked Polyethylene (XLPE) cable has always been related to the byproducts such as acetophenone, a-methylstyrene and cumyl alcohol. In this paper, the argument is to be justified. Space charge formation in cumyl alcohol soaked Low Density Polyethylene (LDPE) is presented and compared with that of acetophenone and a-methylstyrene soaked LDPE. Cumyl alcohol causes charge accumulation of both charge polarities with heterocharges appeared when the sample is stressed at low voltage. The total charge accumulated as well as the charge decay in the clean LDPE sample are then compared to that of the chemicals soaked LDPE films. Charge mobility values in all samples were calculated from the decay characteristics and the results reveal that the byproduct chemicals accelerate the decay process in LDPE film, due to their high charge mobility. Since the byproduct chemicals change the space charge decay behavior of LDPE, it is suggested that the chemicals modify the trapping characteristics of LDPE. This is possible either by superseding the deep traps in insulator with shallow traps from the chemicals, or simply adding up the number of shallow traps in the insulator.

Classical electron-beam resists such as poly(methyl methacrylate) (PMMA) and Nippon Zeon's ZEP function as high resolution and low roughness positive resists on the basis of radiation induced main chain scission to reduce the molecular weight while chemical amplification resists utilized in device manufacturing function on the basis of acidcatalyzed deprotection to change the polarity. In an attempt to increase the resolution and reduce the line roughness of chemical amplification resists, we prepared copolymers that undergo radiation induced main chain scission and acidcatalyzed deprotection. In another word, we wanted to increase the sensitivity of the PMMA resist by incorporating the acid-catalyzed deprotection mechanism in polymers that undergo main chain scission, maintaining the high resolution and low roughness of PMMA. To synthesize such hybrid resist polymers, we selected α-substituted acrylates and α- substituted styrenes. The former included methyl methacrylate (MMA), t-butyl methacrylate (TBMA), methyl α- fluoroacrylate (MFA), t-butyl α-fluoroacrylate (TBFA), and t-butyl α-trifluoromethylacrylate (TBTFMA) and the latter α-methylstyrene (αMEST), α-methyleneindane (αMEIN), and α-methylenetetralin (αMETL). The α-substituted tbutyl acrylic esters were copolymerized with the methyl esters and also with α-substituted styrenic monomers using 2, 2'-azobis(isobutyronitrile) (AIBN). Hybrid resists were formulated by adding a photochemical acid generator and a base quencher to the copolymers and developers were selected by studying the dissolution behavior of unexposed and 254 nm exposed resist films using a quartz crystal microbalance (QCM). In addition to the difference in the imaging mechanism, PMMA and ZEP differ from the chemical amplification resists in developers; organic solvent vs. aqueous base. We were interested in looking also into the influence of the developer on the lithographic performance. Contrast curves were generated by exposing the resist films to 100 keV electron beams and by changing the postexposure bake temperature (PEB) on a thermal gradient hot plate (TGP). The resists were imaged on our Leica 100 keV electron-beam system and line roughness was measured.

In this report the pulsed elcetroacoustic (PEA) technique was employed to examine the space charge pattern in acetophenone and alpha-methylstyrene soaked low-density polyethylene (LDPE) samples. The samples were stressed at three different voltages; 5 kV, 8 kV and 10 kV, and the charge patterns in the sample bulk were compared with that obtained from the clean LDPE. These chemicals are observed to assist the transportation of the charges in the sample bulk. Each of these chemicals is in favour of different charge polarity. It seems that acetophenone assists the transportation of negative charges meanwhile the transportation of positive charges is assisted by the alpha-methylstyrene. It is proposed that the chemicals provide shallow traps that aid the movement of the charges.

Summary: This work deals with modeling the terpolymerization of styrene, α-methylstyrene and methyl methacrylate in the presence of an inhibitor. The model used is a “tendency model” based on the kinetics of the complex elementary chemical reactions both in the aqueous phase and in the particles. It considers the reversible propagation of α-methylstyrene and the main physical phenomena occurring during the process, i.e., (i) partitioning of monomers, surfactant and inhibitor between the aqueous phase, polymer particles, monomer droplets and micelles; (ii) homogeneous and micellar nucleation; (iii) radical absorption and desorption; (iv) gel and glass effects. The main kinetic parameters of the model are estimated on the basis of batch experimental data in order to be able to describe the complete picture of this complex process. The model can be used to predict (with good precision) the global monomer conversion, number and weight-average molecular weight, the average diameter and number of polymer particles and the glass transition temperature, and consequently to study the effects of AMS on conversion and terpolymer and latex characteristics. Comparison of experimental and simulated results of the weight-average molecular weight versus conversion for the emulsion terpolymerization of styrene, alpha methylstyrene and methyl methacrylate at 60 °C.

We have examined the effects of acetophenone and /spl alpha/-methylstyrene on the space charge evolution in PE. The samples tested are additive-free LDPE sheets. The important conclusions obtained are as follows: (1) Positive charges are easy to migrate from the byproduct-existing region to the non-existing region while negative charges are difficult. (2) Positive charge migration is easier in the LDPE sheet soaked into /spl alpha/-methylstyrene than in the one soaked into acetophenone, which is probably due to the difference in permeation velocity of the two byproducts. (3) The values of mobility and conductivity calculated from the space charge profiles agree with the assumption that ionic carriers are responsible for the conduction in the byproduct-existing region.

All planned National Ignition Facility (NIF) capsule targets except machined beryllium require a plastic mandrel upon which the ablator is applied. This mandrel must at least meet if not exceed the symmetry and surface finish requirements of the final capsule. The mandrels are produced by a two-step process. In the first step a thin-walled poly({alpha}-methylstyrene)(P{alpha}MS) shell is produced using microencapsulation techniques. This shell is overcoated with 10 to 15 {micro}m of glow discharge polymer (GDP) and then pyrolyzed at 300 C. This pyrolysis causes the P{alpha}MS to depolymerize to gas phase monomer that diffuses away through the more thermally stable plasma polymer shell, which retains all the symmetry of the original P{alpha}MS shell. Thus our challenge has been to produce 2-mm-diameter P{alpha}MS shells to serve as these initial ''decomposable'' mandrels that meet or exceed the current NIF design specifications. The basic microencapsulation process used in producing P{alpha}MS mandrels involves using a droplet generator to produce a water droplet (Wl) encapsulated by a fluorobenzene solution of P{alpha}MS (O), this compound droplet being suspended in a stirred aqueous bath (W2). Historically this bath has contained poly(vinyl alcohol) (PVA, 88% hydrolyzed, mol. wt. {approx}25,000 g/mol) to prevent agglomeration of the initially fluid compoundmore » droplets. As the compound droplets are stirred in the bath, the fluorobenzene solvent slowly dissipates leaving a solid P{alpha}MS shell. The internal water is subsequently removed by low temperature drying. We found using these techniques that 2-mm shells could easily be produced, however their low mode sphericity did not meet design specifications. In our last published report we detailed how replacement of the PVA with poly(acrylic acid) (PAA) resulted in a major improvement in sphericity due to a greatly increased interfacial tension between the bath and the compound droplet, relative to the use of PVA as the bath additive. P{alpha}MS mandrels produced using PAA in the bath along with slow curing to suppress Marangoni convection that was perturbing the mode 10 to 20 symmetry resulted in 2-mm-diameter P{alpha}MS shells with mode 2 out-of-round{sup 10} (OOR) of {approx}0.5 {micro}m (as well as non-concentricity (NC) < 1%) which meet the capsule design requirements. A representative set of equatorial traces produced by our AFM-based Spheremapper along with the computed power spectrum is shown in Figure 1 for an average shell. Although the power spectrum is at or below the design specification at nearly all modes one can see in the traces some degree of roughness which manifests itself at the very high modes in the power spectrum.« less

ÖZET KÖPÜK POLİSTİRENİN CC-METİLSTİREN VE MUHTELİF TİPTE SİLİKONLARLA MODİFİKASYONU Stiren homopolimerinin bir ortalama yoğunluk modifikasyonu olan köpük polistiren (KPS), süspansiyon polimerizasyonu ile üretilen polistiren taneciklerine pentan (ve/veya izomerleri) emdirilmesi ile elde edilir. Bu yöntemle elde edilen genleşebilir polistiren tanecikleri, 0.4-3 mm arasında değişen bir tanecik dağılımına sahiptirler. Pentan emdirilmiş genleşebilir polistiren tanecikleri, su buharı vasıtasıyla şişirilerek istenilen tanecik yoğunluğuna ulaşılır ve ekstrüzyon ve enjeksiyonlu kalıplama yöntemleriyle işlenir. Endüstride tanecik dağılımına göre farklı amaçlarda kullanılır. Başlıca kullanım alanları: Isı ve ses izolasyonu, ambalajlama, özel ürünlerin ince kalıplama yöntemi ile üretilmesi, tarım sektöründe toprak hafıfleştirilmesi ve hafif beton bloklarının üretilmesidir. Genleşebilir polistiren taneciklerinin ortalama tanecik boyutunun 1-1.4 mm arasında olması ve ortalama tanecik dağılımının mümkün olduğunca l'e yakın olması üreticiler tarafından istenilen özelliklerin başında gelmektedir. Genleşebilen polistiren taneciklerinin su buharı ile şişirilmesiyle elde edilen köpük polistirenin homojen hücre büyüklüğü ve dağılımı, boyutsal kararlılık, ısıl ve mekanik özeliklerin kulanım amacına uygun olması, pürüzsüz ve parlak yüzey görünümü, kalıntı pentan ve monomer miktarının az olması ve istenildiği taktirde yanmazlık özelliklerine sahip olması beklenir. Bu çalışmada köpük polistirenin, bazı yardımcı kimyasallar kullanılarak camsı geçiş sıcaklığının artırılması ve yüzey özelliklerinin geliştirilmesi amaçlanmıştır. Polimerizasyon koşulları Tablo 1' de görülmektedir. Komonomer olarak cc-metilstiren ile modifikasyon: a-metilstiren homopolimerinin camsı geçiş sıcaklığı 170°C civarındadır ve polistirene göre oldukça yüksektir. Ancak a-metilstirenin serbest radikal polimerleşmesi, sterik engelleme yüzünden xvıoldukça zordur ve endüstriyel uygulaması yoktur. Bu yüzden genellikle stirenin polimerleşmesinde komonomer olarak kullanılır, a-metilstiren KPS'nin camsı geçiş sıcaklığını yükseltmek amacıyla % 1; 2.5 ve 5 ağr. oranlarında kullanılmıştır. Reaktif katkı maddesi olarak kullanılabilen V-Si 2250 ile modifikasyon: V-Si 2250, 2100 g/mol molekül ağırlığında bir çeşit silikon akrilat prepolimeridir. Yapısındaki silikon akrilat grubundan dolayı, polimer zincirine katılabildiğinden, çok küçük katkı miktarlarıyla bile polimerin yüzey özelliklerinin geliştirilmesinde kullanılabilir. Bu çalışmada % 0.1; 0.25 ; 0.5 ağr. oranlarında V Si 2250 KPS' nin yüzey modifikasyonu için kullanılmıştır. Siloksanlı makro başlatıcı ile modifikasyon: Polidimetilsiloksan içeren yaklaşık 3150 g/mol molekül ağırlıklı diradikalik makro başlatıcı kullanılarak (% 0.1; 0.2; 0.5 ağr.) yapılan modifikasyonda, başlatıcının polimer ana zincirine katılması ve yapısındaki silikon grubunun yüzeye göç ederek yüzeyi parlak ve pürüzsüz hale getirmesi amaçlanmıştır. Sentezlenen standart ve 10 adet modifiye köpük polistiren örneklerine pentan emdirilerek, bu örneklerin şişme özellikleri, çözelti viskoziteleri, ortalama tanecik boyutları ve dağılımları, kalıntı monomer ve pentan miktarları ile serbest akma yoğunlukları incelenmiştir. Bu incelemelerin sonuçları Tablo 2'de verilmiştir. Köpük haline getirilen örneklerin karakterizasyonu ise çeşitli yöntemlerle yapılmıştır. Kompozisyonun belirlenmesi amacı ile infrared analizi (FTIR) ve proton nükleer manyetik rezonans spektroskopisi ('H-NIVIR), molekül ağırlığı ve dağılımı için jel geçirgenlik kromotografısi (GPC), camsı geçiş sıcaklığı ölçümleri için diferansiyel taramalı kalorimetri (DSC), yüzey ve hücre yapılarının belirlenmesi amacı ile de taramalı elektron mikroskobu (SEM) kullanılmıştır. GPC ve DSC sonuçları Tablo 3'te görülebilmektedir. Şekil 1 ve 2 sırasıyla bazı örneklerin SEM mikrograflarını ve NMR spektralarını göstermektedir. ot-metilstiren kullanımı ile KPS'nin camsı geçiş sıcaklığının artırılması hedeflenen örneklerde (EPS. 02-0. 4), çalışma öncesi gravimetrik yöntemle hesaplanan ve kopolimerdeki her % 1 a-metilstiren miktarına karşılık gelen 1 derecelik Tg artışı kısmi olarak gerçeklenmiştir. XVIIV-Si 2250 içeren örneklerde (EPS 05-08) ise, hücre boyutu ve dağılımının yaklaşık olarak homojen olduğu ancak bazı büyük hücreler içerisinde küçük hücrelerin de oluştuğu gözlenmiştir. Yüzey parlaklığı ve pürüzsüzlüğünün sağlandığı görülmüş ancak şişirilmiş taneciklerde bir miktar Ta artışı ile beraber boyutsal kararlılıkta azalma olduğu gözlenmiştir. Makro başlatıcı içeren örneklerde (EPS 09-1 1) yüzey parlaklığı ve pürüzsüzlüğünün V-Si 2250 katkılı örneklere göre daha iyi olduğu gözlenmiştir. Hücre boyutu ve dağılımının tamamen homojen olduğu ve ideal polihedral hücre yapısının sağlandığı gözlenmiştir. Ayrıca pentan emmemiş sert-çekirdek veya boşluk oluşumuna rastlanılmamıştır. % 0.5 içeren örnekte ( EPS 11) ise ilginç olarak, tüm standart ve modifıye KPS örnekleri arasında en yüksek Tg değerine ulaşıldığı gözlenmiştir. Tüm makro başlatıcı katkılı örneklerde boyutsal kararlılık azalmasına rastlanılmamıştır. Tablo 1. Modifiye Köpük Polistiren Örneklerinin Sentez Koşullan (phm*) * 'de monomer (ağırlıkça) a)Benzoil peroksit c)Dikümil peroksit b,Tersiyer butil per benzoat d> Makro başlatıcı XVIIITablo 2. Deneysel Sonuçların Değerlendirilmesi y 5.0 ' 0 J-9 ?0 Figure 2. 'H-NMR (partial) spectrum of sample no. (a) EPS.01, (b) EPS.04, (c) EPS.07, and (d) EPS. 10. xv 112

La precision et la reproductibilite de la methode proposee est etudiee sur des melanges d'homopolymeres et en analysant la variation des resultats obtenus pour des terpolymeres avec la conversion et avec la composition des melanges de monomeres de depart. Les resultats montrent l'applicabilite de la methode

The thermal degradation of poly({alpha}-methylstyrene) in solution was investigated at various temperatures (150-225 C) and polymer concentrations (2.00-20.0 g/L) at 6.8 MPa (1000 psig). The molecular weight distributions (MWDs) of the reacted polymer at these conditions were examined at four different residence times. Experimental data indicated that the polymer degraded to its monomer, {alpha}-methylstyrene. No other degradation products were observed. Continuous-mixture kinetics was used to examine the MWDs and to obtain the rate coefficient for degradation and its activation energy. The rate was first-order in polymer concentration with a rate constant at 225 C of 0.01 min{sup {minus} 1} and an activation energy of 66.5 kJ/mol (16.0 kcal/mol). The maximum conversion observed at 275 C was 1.2%. Hydrogen-donor solvent, tetralin, had no effect on the degradation.