Surface active and aggregation behavior of methylimidazolium-based ionic liquids of type [Cnmim] [X], n?=?4, 6, 8 and [X]?=?Cl?, Br?, and I? in water

The surface active and aggregation behavior of ionic liquids of type [C _n mim][X] (1-alkyl-3-methylimidazolium (mim) halides), where n = 4, 6, 8 and [X] = Cl⁻, Br⁻ and I⁻ was investigated by using three techniques: surface tension, ¹H nuclear magnetic resonance (NMR) spectroscopy, small-angle neutron scattering (SANS). A series of parameters including critical aggregation concentrations (CAC), surface active parameters and thermodynamic parameters of aggregation were calculated. The ¹H NMR chemical shifts and SANS measurements reveal no evidence of aggregates for the short-chain 1-butylmim halides in water and however small oblate ellipsoidal shaped aggregates are formed by ionic liquids with 1-hexyl and 1-octyl chains. Analysis of SANS data analysis at higher concentrations of [C₈mim][Cl] showed that the microstructures consist of cubically packed molecules probably through π–π and hydrogen bond interactions.     

A small-angle neutron scattering study of the ethyl (n-octyl) phosphate micelles in water

Summary Mixed-double chain anionic surfactants, barium- and lithium-salts of ethyl(n-octyl) phosphate (EOP), which are asymmetric in the molecular shape, and a series of identical chain di-n-alkyl phosphate lithium salts have been synthezized. The limiting partial molar volume of a PO ₄ ^– group (23.43±0.41 cm³ mol^–1) for use in small-angle neutron scattering analysis was determined by density measurements of a series of identical chain di-n-alkyl phosphate lithium salts. For lithium EOP-D₂O system, a critical micellar concentration (2.3 wt%) was determined by³¹P NMR spectra. The micellar shape and size in the EOP-water binary system has been investigated by using small-angle neutron scattering (SANS) spectra. It has been found that the micelles of barium EOP in water have the shape of a prolate spheroid and aggregation numbers (n) equal to 48 at 23°C and 52 at 50°C. For the lithium EOP-micellar system, it has been found that the minimum micelle with an aggregation numbern=21 is spherical and micellar growth and variation from the spherical to the prolate shape might occur with an increase in concen tration above the CMC.     

Kinetics and mechanism of the ring opening polymerization of (R,S)-β-butyrolactone initiated with dibutylmagnesium

Ring opening polymerization (ROP) of (R,S)-β-butyrolactone (BL) using dibutylmagnesium (Bu₂Mg) as initiator was investigated both in bulk and in solution. The synthetic poly-3-hydroxybutyrates (P3HB) were characterized by ¹H NMR, ¹³C NMR, FT-IR and GPC. Effects of molar ratio of initiator to monomer, reaction temperature and time on the monomer conversion and the polymer molecular weight and its distribution were discussed. The kinetics of the solution polymerization of BL was examined and showed a first order both in monomer concentration and initiator concentration. The end groups analysis suggested that the monomer inserted into the growing chain proceeding through the coordination-insertion mechanism based on the acyl-oxygen bond scission rather than the alkyl-oxygen bond cleavage of the BL ring. Furthermore, a possible mechanism for the initiation and propagation procedures of P3HB synthesized from BL with Bu₂Mg was proposed.     

13C and 1H NMR analysis of structural defects in PVC: Application to the production of defects at various polymerization stages

High resolution ¹H and ¹³C NMR data were obtained on PVC and PVC reduced with Bu₃SnH. The reduction is never complete and CH₂Cl groups preferentially remain. It causes almost complete formation of cyclopentane structures from both internal and chain end unsaturation. ¹H NMR gives total unsaturation as well as chain end unsaturation except if there are interferences with initiator residues; in that case, its combination with ¹³ C NMR of reduced PVC gives the chain end unsaturation. By the last method short branches and long ends are determined. Residual primary chlorine in all kinds of branches (methyl, ethyl, butyl, long ends) is taken into account. Long end contents are to be corrected (factor around 1.5), due to incomplete relaxation in standard analysis conditions. ¹H NMR of reduced PVC can be used to get the total non-reduced structures, both -CH₂Cl and -CHCl-. PVC was prepared by suspension or solution (trichlorobenzene) polymerization at 55° C, using dicetyl peroxydicarbonate as an initiator. The initiator residue content is higher in suspension PVC at very low conversion, and then levels off at a low value; in solution polymerization, it chiefly depends on the monomer/initiator ratio. At low conversion, more chain end and less short branches are present in suspension polymerization. Otherwise, only the butyl branch content shows a definite trend to increase with conversion. In solution polymerization, the number of defects is chiefly dependent on the initial monomer concentration; it is generally much higher than in suspension, except for the chloromethyl branches where both processes give about the same results.     

Facile synthesis and characterization of hyperbranched poly(ether amide)s generated from Michael addition polymerization of in situ created AB2 monomers

A new straightforward strategy for synthesis of novel hyperbranched poly (ether amide)s from readily available monomers has been developed. By optimizing the reaction conditions, the AB₂‐type monomers were formed dominantly during the initial reaction stage. Without any purification, the AB₂ intermediate was subjected to further polymerization in the presence (or absence) of an initiator, to prepare the hyperbranched polymer‐bearing multihydroxyl end‐groups. The influence of monomer, initiator, and solvent on polymerization and the molecular weight (MW) of the resultant polymers was studied thoroughly. The MALDI–TOF MS of the polymers indicated that the polymerization proceeded in the proposed way. Analyses of ¹H NMR and ¹³C NMR spectra revealed the branched structures of the polymers obtained. These polymers exhibit high‐moderate MWs and broad MW distributions determined by gel permeation chromatography (GPC) in combination with triple detectors, including refractive index, light scattering, and viscosity detectors. In addition, the examination of the solution behavior of these polymers showed that the values of intrinsic viscosity [η] and the Mark–Houwink exponent α were remarkably lower compared with their linear analogs, because of their branched nature. © 2007 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 45: 4309–4321, 2007     

Living polymerization of D,L‐3‐methylglycolide initiated with bimetallic (Al/Zn) μ‐oxo alkoxide and copolymers thereof

D,L ‐3‐Methylglycolide (MG) was successfully polymerized with bimetallic (Al/Zn) μ‐oxo alkoxide as an initiator in toluene at 90 °C. The effect of the initiator concentration and monomer conversion on the molecular weight was studied. It is shown that the polymerization of MG follows a living process. A kinetic study indicated that the polymerization approximates the first order in the monomer, and no induction period was observed. ¹H NMR spectroscopy showed that the ring‐opening polymerization proceeds through a coordination–insertion mechanism with selective cleavage of the acyl–oxygen bond of the monomer. On the basis of ¹H NMR and ¹³C NMR analyses, the selective cleavage of the acyl–oxygen bond of the monomer mainly occurs at the least hindered carbonyl groups (P₁ = 0.84, P₂ = 0.16). Therefore, the main chain of poly(D,L ‐lactic acid‐co‐glycolic acid) (50/50 molar ratio) obtained from the homopolymerization of MG was primarily composed of alternating lactyl and glycolyl units. The diblock copolymers poly(ϵ‐caprolactone)‐b‐poly(D,L ‐lactic acid‐alt‐glycolic acid) and poly(L ‐lactide)‐b‐poly(D,L ‐lactic acid‐alt‐glycolic acid) were successfully synthesized by the sequential living polymerization of related lactones (ϵ‐caprolactone or L ‐lactide). ¹³C NMR spectra of diblock copolymers clearly show their pure diblock structures. © 2000 John Wiley & Sons, Inc. J Polym Sci A: Polym Chem 39: 357–367, 2001     

Merging Styrene and Diene Structures to a Cyclic Diene: Anionic Polymerization of 1-Vinylcyclohexene (VCH)

We report the first anionic polymerization of 1-vinylcyclohexene (VCH). This structure may be considered as an intermediate between dienes and styrene. The polymerization of this cyclic 1,2-disubstituted 1,3-diene proceeded quantitatively in cyclohexane at 25 °C with sec-butyllithium as an initiator. The obtained polymers have well-controlled molecular weights in the range of 5 to 142 kg mol⁻¹, controlled by the molar ratio of monomer and initiator, with narrow molecular weight distributions (Đ<1.07–1.20). In situ ¹H NMR kinetic characterization revealed a weak gradient structure for the copolymers of styrene and VCH, (r_Sty=2.55, r_VCH=0.39). P(VCH) obtained in cyclohexane with sec-BuLi as an initiator showed both 1,4- and 3,4-incorporation mode (ratio: 64 : 36). It was demonstrated that the microstructure of the resulting P(VCH) can be altered by the addition of a modifier (THF), resulting in increasing 3,4-microstructure (up to 78 %) and elevated glass-transition temperature up to 89 °C. Thus, the monomer VCH polymerizes carbanionically like a diene, however leading to rigid polymers with high glass transition temperature, which provides interesting options for combination with other dienes to well-defined polymer architectures and materials.     

Ring‐opening polymerization of 1,4‐dioxan‐2‐one initiated by lanthanum isopropoxide in bulk

Lanthanum isopropoxide (La(OiPr)₃) has been synthesized and employed for ring‐opening polymerization of 1,4‐dioxan‐2‐one in bulk as a single‐component initiator. The influences of reaction conditions such as initiator concentration, reaction time, and reaction temperature on the polymerization were investigated. The kinetics indicated that the polymerization is first‐order with respect to the monomer concentration. The Mechanistic investigations according to ¹H NMR spectrum analysis demonstrated that the polymerization of PDO proceeded through a coordination‐insertion mechanism with a rupture of the acyl‐oxygen bond of the monomer rather than the alkyl‐oxygen bond cleavage. © 2008 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 46: 5214–5222, 2008     

Atom Transfer Radical Polymerization of Styrene with 5‐Chloromethyl‐2‐hydroxy‐benzaldehyde as Initiator

Abstract

Atom transfer radical polymerization (ATRP) of styrene (St) proceeded using 5‐chloromethyl‐2‐hydroxy‐benzaldehyde as initiator, CuCl as catalyst, and N,N,N′,N′,N′‐pentamethyldiethyltriamine (PMDETA) as ligand. The results show that the polymerization is a first order reaction with respect to monomer concentration. The polymerization displayed living character as evidenced by a liner increase of monomer weight with conversation and a relatively narrow distribution (M _n/M _w ranges from 1.25 to 1.50). The end structure of PSt was analyzed by ¹H‐NMR, and PSt initiated MMA to form block copolymer (PSt‐b‐PMMA), which also proved that the polymerization could be controlled. The effects of reaction temperature and monomer to initiator mole ratio on the polymerization displayed living character were discussed.     

One‐step synthesis of block‐graft copolymers via simultaneous reversible‐addition fragmentation chain transfer and ring‐opening polymerization using a novel macroinitiator

One‐step synthesis of block‐graft copolymers by reversible addition‐fragmentation chain transfer (RAFT) and ring‐opening polymerization (ROP) by using a novel initiator was reported. Block‐graft copolymers were synthesized in one‐step by simultaneous RAFT polymerization of n‐butylmethacrylate (nBMA) and ROP of ε‐caprolacton (CL) in the presence of a novel macroinitiator (RAFT‐ROP agent). For this purpose, first epichlorohydrin (EPCH) was polymerized by using H₂SO₄ via cationic ring‐opening mechanism. And then a novel RAFT‐ROP agent was synthesized by the reaction of potassium ethyl xanthogenate and polyepichlorohydrin (poly‐EPCH). By using the RAFT‐ROP agent, poly[CL‐b‐EPCH‐b‐CL‐(g‐nBMA)] block‐graft copolymers were synthesized. The principal parameters such as monomer concentration, initiator concentration, and polymerization time that affect the one‐step polymerization reaction were evaluated. The block lengths of the block‐graft copolymers were calculated by using ¹H‐nuclear magnetic resonance (¹H NMR) spectrum. The block length could be adjusted by varying the monomer and initiator concentrations. The characterization of the products was achieved using ¹H NMR, Fourier‐transform infrared spectroscopy, gel‐permeation chromatography, thermogravimetric analysis, differential scanning calorimetry, elemental analysis, and fractional precipitation (γ) techniques. © 2013 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2013, 51, 2651–2659     

Radical polymerization of vinyl thiocyanatoacetate: Participation of group‐transfer mechanism

Vinyl thiocyanatoacetate (VTCA) was synthesized, and its radical polymerization behavior was studied in acetone with dimethyl 2,2′‐azobisisobutyrate (MAIB) as an initiator. The initial polymerization rate (R_p) at 60 °C was expressed by R_p = k[MAIB]^0.6±0.1 [VTCA]^1.0±0.1 where k is a rate constant. The overall activation energy of the polymerization was 112 kJ/mol. The number‐average molecular weights of the resulting poly (VTCA)s (1.4–1.6 × 10⁴) were almost independent of the concentrations of the initiator and monomer, indicating chain transfer to the monomer. The chain‐transfer constant to the monomer was estimated to be 9.6 × 10^?3 at 60 °C. According to the ¹H and ¹³C NMR spectra of poly (VTCA), the radical polymerization of VTCA proceeded through normal vinyl addition and intramolecular transfer of the cyano group. The cyano group transfer became progressively more important with decreasing monomer concentration. © 2002 John Wiley & Sons, Inc. J Polym Sci Part A: Polym Chem 40: 573–582, 2002; DOI 10.1002/pola.10137     

Kinetic studies on the imine base/isocyanate‐induced radical polymerization of vinyl monomers

Specific imine bases (IB) in conjunction with various isocyanates (IC) mediate the radical polymerization of radically polymerizable monomers such as methyl methacrylate (MMA). Advantageously, the 2‐(methylmercapto)‐2‐thiazoline MMT/IC combination as initiator works even at room temperature for polymerization of MMA. The coefficients a, b, and c of the basic rate law of monomer consumption d[M]/dt = k_p·[IC]^a·[IB]^b·[M]^c were determined. The order a has been determined to 0.5 showing the root law of radical polymerization with respect to the IC component as initiator. Moreover, b and c amount 1. The initiator combination MMT/ IC was applied to determine the influence of the molecular structure of the IC on the rate of monomer conversion. For aromatic isocyantes, the gross rate constant of monomer consumption correlates with the Hammet constant of aromatic substituents. The activation energies of the gross polymerization rate constant of several initiator mixtures were determined whereby the value of E_A,Br was found to be between typical values of radical polymerization initiated by photochemical reactions (～20 kJ/mol) and commonly used thermal decomposing initiators (～80 kJ/mol). Presumptions on the initiating and terminating step of the IB/IC mediated polymerization were done by means of electrospray ionization mass spectrometry, NMR spectroscopy, and the elemental composition of the head and end group of the resulting polymers. © 2012 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem, 2012     

Titanium complexes of dialkanolamine ligands as initiators for living ring‐opening polymerization of ε‐caprolactone

The titanium complexes with one ( 1a , 1b , 1c ) and two ( 2a , 2b ) dialkanolamine ligands were used as initiators in the ring‐opening polymerization (ROP) of ε‐caprolactone. Titanocanes 1a and 1b initiated living ROP of ε‐caprolactone affording polymers whose number‐average molecular weights (M_n) increased in direct proportion to monomer conversion (M_n ≤ 30,000 g mol^?1) in agreement with calculated values, and were inversely proportional to initiator concentration, while the molecular weight distribution stayed narrow throughout the polymerization (M_w/M_n ≤ 1.2 up to 80% monomer conversion). ¹H‐NMR and MALDI‐TOF‐MS studies of the obtained poly(ε‐caprolactone)s revealed the presence of an isopropoxy group originated from the initiator at the polymer termini, indicating that the polymerization takes place exclusively at the Ti–OⁱPr bond of the catalyst. The higher molecular weight polymers (M_n ≤ 70,000 g mol^?1) with reasonable MWD (M_w/M_n ≤ 1.6) were synthesized by living ROP of ε‐caprolactone using spirobititanocanes ( 2a , 2b ) and titanocane 1c as initiators. The latter catalysts, according MALDI‐TOF‐MS data, afford poly(ε‐caprolactone)s with almost equal content of α,ω‐dihydroxyl‐ and α‐hydroxyl‐ω(carboxylic acid)‐terminated chains arising due to monomer insertion into “Ti–O” bond of dialkanolamine ligand and from initiation via traces of water, respectively. © 2010 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 48: 1230–1240, 2010     

Atom Transfer Radical Polymerization of Styrene Using Multifunctional Iniferter Reagents as Initiators

Summary: Two multifunctional iniferters, 1,4-bis-(α-N,N-diethyldithiocarbamyl-isobutyryloxy)-benzene (BDCIB) and 1,3,5-tris-(α-N,N-diethyldithiocarbamyl-isobutyryloxy)-benzene (TDCIB), were successfully synthesized and used as initiators to initiate the polymerization of styrene in the presence of a CuBr/PMDETA complex. The polymerization results demonstrated that the kinetic plots in all cases were first-order to the monomer, the molecular weight of the polymers increased linearly with the monomer conversion; meanwhile, the molecular weight distribution of the polymer was kept to a very low value (M_w/M_n ≤ 1.35). Furthermore, the measured molecular weights were very close to the calculated values, which indicated the high efficiency of the initiator for the polymerization of styrene. The effect of catalyst concentration and initiator concentration was not obvious and the influence of polymerization temperature was apparent, and the polymerization rate increased with the polymerization temperature. The results of chain-extension and ¹H NMR analysis proved that the polymer obtained was capped with diethylthiocarbamoylthiy (DC) group.     

三(2,4,6-三甲基苯氧基)稀土配合物引发DL-丙交酯开环聚合特征与机理的研究

Tris(2,4,6-trimethylphenolate) lanthartide [Ln(OTMP)3] has been prepared and employed for ring-opening polymerization of D,L-lactide (LA) as single-component catalysts. The characteristics, kinetics and mechanism were examined. The polymerization is first-order with respect to monomer and initiator concentration, and the overall activation energy amounts to 62.9 kJ/mol. DSC curve disclosed the random structure of PLA. ^1H NMR spectrum analysis demonstrates that the polymerization of LA proceeded through acyl-oxygen bond cleavage.     

Comparison of oil-soluble and water-soluble initiation of styrene polymerization in a three-component microemulsion

The polymerization of styrene in three-component oil-in-water microemulsions made with the cationic surfactant dodecyltrimethylammonium bromide is studied by dilatometry and quasielastic light scattering as a function of type and concentration of initiator. Fast polymerization rates, high conversions, and high molecular weight polymers are achieved with both oil-soluble (AIBN) and water-soluble (potassium persulfate) initiators. The rate of polymerization shows initiation and termination intervals, but no constant-rate interval is observed. Stable monodisperse microlatexes are obtained with both types of initiators. For both AIBN and potassium persulfate, polystyrene molecular weight is proportional to initiator concentration [I]^–0.4 and particle radii decrease as [I]^–0.2. Polymerization initiation occurs in or at the microemulsion droplets, and polymer particles grow by recruiting monomer and surfactant from uninitiated swollen micelles.     

Fluorocarbon-hydrocarbon incompatibility in micellar polymerizations

A new approach to micellar polymerization is described. It is well known that hydrocarbons and fluorocarbons exhibit local phase segregation (demixing) owing to mutual antipathy; here this effect is employed in monomer swollen micelles with appropriate combinations of hydrocarbon and fluorocarbon monomers and surfactants. A matrix of these hydro- and fluorocarbon components has been investigated to delineate the effects of H–F antipathy on the outcomes of polymerization reactions to generate nanolatices of different size (and possibly morphology). Phase diagrams, ¹H NMR and small-angle neutron (SANS) data have been generated to characterize the systems, indicating new routes to influence nanolatex formation.     

苯氧铜/正丁基锂体系引发MMA负离子聚合及其活性特征的研究

采用苯氧铜/正丁基锂(PhOCu/n-BuLi)体系引发MMA聚合, 通过GPC, ¹H NMR对聚合物进行了表征. 实验结果表明, 该体系聚合反应速度较快, 温度、引发体系组成是影响聚合物分子量及其分布、单体转化率、引发剂引发效率、聚合物的立构规整性的主要因素; －40 ℃时分子量分布比较窄, 但引发效率也比较低(大约15%). 低引发效率、宽分子量分布与引发剂的聚集状态有关. 分子量与单体浓度、引发剂浓度的关系说明, 该体系具有一定程度的活性聚合特点.     

Synthesis of well‐defined naphthalene and photo‐labile group‐labeled polystyrene via ATRP

The atom transfer radical polymerizations of styrene were successfully carried out in bulk and solution, respectively, at 115 °C, with a novel photoiniferter reagent, (1‐naphthyl)methyl N,N‐diethyldithiocarbamate (NMDC), as an initiator in the presence of copper (I) bromide and N,N,N′,N″,N″‐pentamethyldiethylenetriamine. The results showed that NMDC was an effective initiator with high initiation efficiency for ATRP of St. The polymerization rate was first‐order with respect to the monomer concentration and the molecular weights of the obtained polystyrene (PS) increased linearly with the monomer conversion, with very narrow molecular weight distributions (M_w/M_n = 1.07–1.29). The functionalized naphthalene‐labeled PS bearing N,N‐(diethylamino)dithiocarbamoyl group which was confirmed by ¹H NMR analysis, and chain extension of the PS exhibited fluorescence and ultraviolet absorption in chloroform (CHCl₃). © 2005 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 44: 510–518, 2006     

Synthesis of poly(glycerol)‐block‐poly(methyl acrylate) multi‐arm star polymers

Novel polyfunctional macroinitiators for atom transfer radical polymerization (ATRP) were obtained via esterification of hyperbranched polyglycerol (PG) (M_n = 4 770 g/mol, M_w/M_n = 1.5) with 2‐bromoisobutyryl bromide. Such macroinitiators were used in the presence of CuBr/pentamethyldiethylenetriamine (PMDETA) to initiate methyl acrylate (MA) polymerization, resulting in multi‐arm block copolymers with polyether core and 45–55 PMA arms. PMA arm length was controlled via monomer/initiator ratio and conversion (< 35%). Polymers were characterized by ¹H NMR, ¹³C NMR, SEC, membrane osmometry and DSC.