Copolymerization of methylmethacrylate with styrene using triphenylbismuthoniumylide as radical initiator

Bismuthoniumylide‐initiated radical copolymerization of methylmethacrylate with styrene at 60 ± 0.2°C using dioxane as an inert solvent, follows ideal kinetics (R_p ∝ [ylide]^0.5 [MMA]^1.0 [sty]^1.0), and yields alternating copolymer as evident from NMR spectroscopy. The values of reactivity ratios r₁ and r₂, calculated from Finemann–Ross method are 0.48 and 0.45, respectively. The system follows ternary molecular complex mechanism. The radical mode of polymerization has been confirmed by ESR spectroscopy and the effect of hydroquinone. The value of activation energy and k/k_t are 65.0 KJ mol^?1 and 2.5 × 10^?5 l mole^?1 s^?1, respectively. © 2001 John Wiley & Sons, Inc. J Appl Polym Sci 80: 2774–2781, 2001     

Kinetics of the polymerization of methylmethacrylate with 4,4′-azobis (4-cyanopentanol) as initiator

Summary The radical polymerization in bulk of methylmethacrylate in presence of 4,4 azobis(cyanopentanol) (ACP) has been studied at 60°, 67°, 72°, 81° and 84°C. The ratio kp/kt^1/2 has been determined for each of these temperatures, using the molecular weight method. The rates constants of decomposition and the efficiency of (ACP) were calculated from conversion-time curves. The activation energy of the polymerization was obtained from the slope of Arrhenius plot of Rp.     

A rapid synthesis of poly (p-dioxanone) by ring-opening polymerization under microwave irradiation

Summary A rapid synthesis of poly(p-dioxanone) (PPDO) was carried out smoothly and effectively from the monomer p-dioxanone (PDO) with constant microwave powers of 90, 180, 270, and 360 W, respectively, in a microwave oven at a frequency of 2.45 GHz. The temperature of the polymerization ranged from 158 to 198 °C. PPDO with a viscosity-average molecular weight (Mv) of 156,000g/mol and yield of 63% was obtained at 270W for 25 min using 1/1000 (mol/mol) Sn(Oct)₂ as a catalyst, while it took more than 14h to obtain PPDO with high molecular weight and monomer conversion by conventional heating method when Sn(Oct)₂ used as a catalyst. Therefore, it is obvious that the polymerization rate is faster than that of the conventional polymerization method when microwave irradiation is used in polymerization process.     

Poly(p-maleimidostyrene) as a macromolecule initiator for polymerization of styrene-type monomers - Synthesis of block copolymers containing poly(p-maleimidostyrene) with highly reactive pendent maleimido groups

4-Substituted styrenes (substituent: methoxy, methyl, acetoxy, maleimido and none), were cationically polymerized with an initiator system involving poly(p-maleimidostyrene)(PMS) as a macroinitiator, having highly reactive pendent maleimide moieties and a α-chlorobenzyl structure at the polymer end. Using PMS/SnCl₄/tetra-n-butylammmonium chloride initiator system, block copolymers of 4-substituted styrenes onto PMS were obtained in CH₂Cl₂ at 0 °C. As for the polymerization of N-(4-vinylphenyl)maleimide and 4-acetoxystyrene, especially, PMS as the macroinitiator was almost completely utilized for initiation reaction and the polymers having PMS-b-poly(4-substituted styrene) platform with very narrow and unimodal molecular weight distribution were formed in contrast with the case of using 4-methoxystyrene and 4-methylstyrene with stronger electron releasing groups, in which the molecular weight distributions of the formed polymeric materials appeared to be bimodal.     

Study on initiating approach of (3-(tert-butylperoxy)propyl) trimethoxysilane on the polymerization of acrylonitrile as an initiator*

(3-(tert-butylperoxy)propyl) trimethoxysilane (TBPT), is a tailor-made new style silane coupling agent with peroxide group, which have ability of initiating polymerization. This study used TBPT to generate free radical, and initiated the polymerization of acrylonitrile (AN), thereby forming polyacrylonitrile (PAN) in two approaches, thermal initiation system and redox initiation system. Meanwhile this study bonded TBPT onto nano-TiO₂ to get modified nano-TiO₂ by means of the coupling function of TBPT, and then made the peroxide group of the modified nano-TiO₂ decompose and initiate the polymerization of AN in thermal initiation system and redox initiation system respectively. The products were investigated and analyzed by FTIR, XPS and TG. The result showed that on one hand, in the products of the thermal initiation there was PAN, which both attached and unattached to the modified nano-TiO₂; on the other hand, in the products of the redox initiation system the PAN unattached to the modified nano-TiO₂ was produced, while the PAN attached to the modified nano-TiO₂ was not.     

氯乙烯悬浮(本体)聚合用过氧化物引发剂

介绍了氯乙烯(VC)悬浮(本体)聚合常用过氧化引发剂的合成方法，着重阐述引发剂与聚合动力学的关系以及聚合动力学的检测方法。研究了单一和复合引发剂条件下的VC聚合动力学，为优化引发剂体系、缩短聚合时间、提高聚合釜的生产能力提供理论基础。     

Synthesis of polystyrene oligomers by nitroxide‐mediated radical polymerization using diethylketone triperoxide as a multifunctional radical initiator

Styrene oligomers (M_n, 2500–3000 g/mol) with low polydispersity index and containing peroxidic groups within their structure were synthesized using a novel trifunctional cyclic radical initiator, diethylketone triperoxide (DEKTP), through nitroxide‐mediated radical polymerization (NMRP), using OH‐TEMPO. During the synthesis of the polystyrene (PS) oligomers, camphorsulfonic acid (CSA) was used to inhibit the thermal autoinitiation of styrene at the evaluated temperatures (T = 120–130°C). The polymerization rate, which can be related to the slope of the plot of monomer conversion with reaction time, was monitored as a function of OH‐TEMPO, DEKTP, and CSA concentrations. The experimental results showed that all the synthesized polymers presented narrow molecular weight distributions, and the monomer conversion and the molecular weight of the polymers increased as a function of reaction time. Under the experimental conditions, T = 130°C, [DEKTP] = 10 mM, and [DEKTP]/[OH‐TEMPO] = 6.5, PS oligomers containing unreacted O? O sites in their inner structure were obtained. © 2011 Wiley Periodicals, Inc. J Appl Polym Sci, 2012     

Kinetics for free radical solution polymerization of heptadecafluorodecyl (meth)acrylate in supercritical carbon dioxide

Free radical solution polymerization of heptadecafluorodecyl acrylate (HDFDA) and heptadecafluorodecyl methacrylate (HDFDMA) was carried out by using 2,2′-azobisisobutyronitrile (AIBN) as the initiator in supercritical carbon dioxide (scCO₂). We performed solution polymerization with changing initiator concentration, temperature and polymerization time to study the polymerization kinetics. A nonlinear least square method and dead-end theory were used to determine the constant, K (K=(k _p √f)/√k _d k _d ) and initiator decomposition rate constant (k _d ) from experimental data. k _d was measured as 3.77 × 10⁻⁵ s⁻¹ at 62.7°C for poly(HDFDA) and 2.71 × 10⁻⁵ s⁻¹ at 62.5 °C for poly(HDFDMA), respectively, by nonlinear least square method.     

Synthesis of highly isotactic (mm > 0.70) polyacrylonitrile by anionic polymerization using diethylberyllium as a main initiator

An attempt was made to synthesize steroregular polyacrylonitrile (PAN) with a high triad isotacticity (i.e. the content of mm (m, meso)) exceeding 0.70 by the anionic polymerization method. In the stereospecific polymerization of acrylonitrile (AN) initiated by diethylberyllium (Et₂Be) in xylene at 130°C, the (mm) content as well as the viscosity-average molecular weight (MÞ_v) of PAN increased by addition of diisobutylaluminum hydride (i-C₄H₉)₂AlH) as an additive to the polymerization system. Maximum (mm) content, attained in the molar ratio region of (i-C₄H₉)₂AlH/Et₂Be > 1.0, was about 0.73. The stereospecific polymerization of AN was also initiated using a mixture of Et₂Be and di-n-hexylamagnesium ((Et₂Be/(n-C₆H₁₃)₂ Mg system), where both Et₂Be and (n-C₆H₁₃)₂ Mg can induce the stereospecific polymerization of AN at 130°C. The (mm) content of the PAN sample prepared using the Et₂Be/(n-C₆H₁₃)₂ Mg system ((mm) = 0.64) was higher than that of PAN samples synthesized using Et₂Be alone ((mm) = 0.56) and (n-C₆H₁₃)₂Mg alone ((mm) = 0.51) under the same conditions except initiator. A significant difference in ¹³C chemical shifts of α-carbons between Et₂Be (1.35 ppm) and (n-C₆H₁₃)₂Mg (10.72 ppm) dissolved in hydrocarbon solvent at 110°C leads us to the conclusion that when Et₂Be induces the stereospecific polymerization in the Et₂Be/(n-C₆H₁₃)₂Mg system as initiator, the main role of (n-C₆H₁₃)₂Mg is considered to be the suppression of the association of Et₂Be (active site) itself.     

Nucleation mechanism and morphology of polystyrene/Fe3O4 latex particles via miniemulsion polymerization using AIBN as initiator

In this study, oil‐based magnetic Fe₃O₄ nanoparticles were first synthesized by a coprecipitation method followed by a surface modification using lauric acid. Polystyrene/Fe₃O₄ composite particles were then prepared via miniemulsion polymerization method using styrene as monomer, 2,2′‐azobisisobutyronitrile (AIBN) as initiator, sodium dodecyl sulfate (SDS) as surfactant, hexadecane (HD) or sorbitan monolaurate (Span20®) as costabilizer in the presence of Fe₃O₄ nanoparticles. The effects of Fe₃O₄ content, costabilizer, homogenization energy during ultrasonication, and surfactant concentration on the polymerization kinetics (e.g., conversion), nucleation mechanism, and morphology (e.g., size distributions of droplets and latex) of composite particles were investigated. The results showed that at high homogenization energy, an optimum amount of SDS and hydrophobic costabilizer was needed to obtain composite particles nucleated predominately by droplet nucleation mechanism. The morphology of the composite particles can be well controlled by the homogenization energy and the hydrophobicity of the costabilizer. The magnetic composite particles can be made by locating Fe₃O₄ inside the latex particles or forming a shell layer on their PS core surface depending on the aforementioned polymerization conditions. © 2009 Wiley Periodicals, Inc. J Appl Polym Sci, 2009     

Atom transfer radical polymerization of styrene with 2‐(1‐bromoethyl)‐anthraquinone as an initiator

2‐(1‐Bromoethyl)‐anthraquinone (BEAQ) was successfully used as an initiator in the atom transfer radical polymerization of styrene with CuBr/N,N,N′,N′,N″‐pentamethyldiethylenetriamine as the catalyst at 110°C. The polymerizations were well controlled with a linear increase in the molecular weights (M_n's) of the polymers with monomer conversion and relatively low polydispersities (1.1 < weight‐average molecular weight (M_w)/M_n < 1.5) throughout the poly merizations. The resultant polystyrene thus possessed one chromophore moiety (2‐ethyl‐anthraquinone) at the α end and one bromine atom at the ω end, both from the initiator BEAQ. The intensity of UV absorptions of the resultant polymers decreased with increasing molecular weights of the polymers. © 2006 Wiley Periodicals, Inc. J Appl Polym Sci 102: 2081–2085, 2006     

Porous poly(vinyl formal) foam prepared using poly(vinyl alcohol) of low degree of polymerization

Poly(vinyl formal) (PVF) foams are usually prepared using poly(vinyl alcohol) (PVA) of high degree of polymerization, the most reported degree of polymerization being 1700. In the work reported, PVA of low degree of polymerization of 500 was used to prepare PVF foams, which is a great challenge because of the weaker hydrogen bond interaction than that for a higher degree of polymerization. By changing the concentration (from 10 to 20 wt%) of PVA solution, PVF foams were successfully obtained. It was found that a higher PVA concentration prevented foam volume shrinkage and the best concentration was 16 wt%. Scanning electron microscopy showed that the PVF foams had two kinds of pore structures, closed and open cell. The water absorption capacity and thermal properties of the PVF foams were carefully investigated. © 2018 Society of Chemical Industry     

Direct synthesis of syndiotactic-rich poly(N-isopropylacrylamide) via radical polymerization of hydrogen-bond-complexed monomer

Radical polymerization of N-isopropylacrylamide (NIPAAm) in toluene was investigated in the presence of hexamethylphosphoramide (HMPA). We succeeded in directly preparing syndiotactic-rich poly(NIPAAm), the syndiotacticity of which (r=70%) is the highest among those of radically-prepared poly(NIPAAm)s so far reported, by lowering polymerization temperature to −60 °C in the presence of a two-fold amount of HMPA. The NMR analysis revealed that the induced syndiotactic-specificity was ascribed to 1:1 complex formation between NIPAAm and HMPA. Furthermore, thermodynamic analysis described that the induced syndiotactic-specificity was enthalpically achieved.     

Synthesis and characterization of poly(methyl methacrylate) using monofunctional polyhedral oligomeric silsesquioxane as an initiator

POSS/PMMA composite was synthesized by atom transfer radical polymerization (ATRP) at 110 °C using commercial POSSCl as an initiator and CuCl/2,2′-bipyridine as catalyst system. The structures of POSS/PMMA and POSSCl were characterized by Fourier transfer infrared spectroscopy, Nuclear magnetic resonance spectroscopy, Ger permeation chromatography, X-ray diffraction and X-ray photoelectron spectroscopy, which confirmed that Si–Cl bond on POSS cage could successfully initiate the ATRP of methyl methacrylate, so there is only one POSS unit in a PMMA chain. The thermal properties of POSS/PMMA were investigated by Differential scanning calorimetry and Thermogravimetric analysis, the results show that the incorporation of POSS cage results in the enhancement of the glass transition temperature and the decomposition temperature of PMMA, which is mainly attributed to the mono-dispersion of POSS in PMMA matrix at molecular lever.     

Heterotactic poly(N-isopropylacrylamide) prepared via radical polymerization in the presence of fluorinated alcohols

Radical polymerization of N-isopropylacrylamide in toluene at −40 °C in the presence of fourfold amounts of fluorinated alcohols was investigated. The ¹³C NMR analysis of the obtained polymers suggested that the addition of fluorinated alcohols induced heterotactic specificity in radical polymerization of NIPAAm, although syndiotactic poly(NIPAAm)s were obtained by adding alkyl alcohols as we have previously reported. To the best of our knowledge, this is the first synthesis of heterotactic poly(NIPAAm).     

Ring‐opening polymerization of lactones using RuCl2(PPh3)3 as initiator: Effect of hydroxylic transfer agents

ε‐Caprolactone and δ‐valerolactone were polymerized in bulk at 150°C using the ruthenium(II) complex RuCl₂(PPh₃)₃ as initiator in the presence of 1,3‐propanediol (PD) with a series of alcohols as coinitiators. Polymerization of lactones proceeds via ruthenium(II) alkoxide active centers. ¹H‐NMR analysis revealed that the ruthenium complex reacted with the alcohol, generating in situ a ruthenium alkoxide. This species became a more active initiator of ring‐opening polymerization than was RuCl₂(PPh₃)₃. The obtained polylactones were characterized by ¹H‐ and ¹³C‐NMR and matrix‐assisted laser desorption ionization time‐of‐flight (MALDI‐TOF). The results showed the formation had occurred of α,ω‐telechelic PCL and PVL diols, in which PD had been incorporated into the polymer backbone. Depending on the nature of the alcohol used as coinitiator, PCLs with different end groups could be synthesized. Insertion of an alcohol as an end group (benzyl alcohol, n‐octanol, or isopropanol) or into the polymeric backbone (propanediol) provided support for the conclusion that a classical coordination–insertion mechanism was operating during lactone polymerization. © 2005 Wiley Periodicals, Inc. J Appl Polym Sci, 2006     

Synthesis of densely grafted copolymers by nitroxide-mediated radical polymerization of styrene using poly(phenylacetylene)s as a macroinitiator

Poly(phenylacetylene)s carrying alkoxyamine moieties in the side chain were prepared by Rh-catalyzed homopolymerization of 1-(4-ethynylphenyl)-1-(2,2,6,6-tetramethyl-1-piperidinyloxyl)ethane (1) and random copolymerization of 1 and 4-methoxy-1-ethynylbenzene (2a) or 4-decyloxy-1-ethynylbenzene (2b). ¹H NMR spectra showed that the poly(phenylacetylene)s adopted a cis-transoid structure. Using the poly(phenylacetylene)s as the macroinitiator the nitroxide-mediated radical polymerization of styrene (St) was carried out at 120 °C to yield densely grafted copolymers as a light yellow powder. The side chain lengths of the graft copolymers were determined by both ¹H NMR and conversion of St, which agreed with each other. The SEC profiles of the graft copolymers were unimodal at low conversions but were not unimodal at high conversion: a shoulder was observed in the high molecular=weight region and a small peak was observed in the low molecular=weight region. ¹H NMR measurements of the graft copolymers indicated that the copolymers adopted a trans-transoid structure, revealing that isomerization from cis-transoid to trans-transoid forms took place during the polymerization of St at 120 °C.     

Scanned Probe Oxidation on p-GaAs(100) Surface with an Atomic Force Microscopy

Locally anodic oxidation has been performed to fabricate the nanoscale oxide structures on p-GaAs(100) surface, by using an atomic force microscopy (AFM) with the conventional and carbon nanotube (CNT)-attached probes. The results can be utilized to fabricate the oxide nanodots under ambient conditions in noncontact mode. To investigate the conversion of GaAs to oxides, micro-Auger analysis was employed to analyze the chemical compositions. The growth kinetics and the associated mechanism of the oxide nanodots were studied under DC voltages. With the CNT-attached probe the initial growth rate of oxide nanodots is in the order of ~300 nm/s, which is ~15 times larger than that obtained by using the conventional one. The oxide nanodots cease to grow practically as the electric field strength is reduced to the threshold value of ~2 × 10⁷ V cm⁻¹. In addition, results indicate that the height of oxide nanodots is significantly enhanced with an AC voltage for both types of probes. The influence of the AC voltages on controlling the dynamics of the AFM-induced nanooxidation is discussed.