Novel Copolymers of Styrene. 1. Alkyl Ring-Substituted Butyl 2-Cyano-3-Phenyl-2-Propenoates

Novel trisubstituted ethylenes, alkyl ring-substituted butyl 2-cyano-3-phenyl-2-propenoates, RPhCH=C(CN)CO₂C₄H₉ (where R is 2-methyl, 3-methyl, 4-methyl, 2-ethyl, 4-ethyl, 4-butyl, 4-t-butyl, 4-i-butyl) were prepared and copolymerized with styrene. The monomers were synthesized by the piperidine catalyzed Knoevenagel condensation of ring-substituted benzaldehydes and butyl cyanoacetate, and characterized by CHN analysis, IR, ¹H and ¹³C-NMR. All the ethylenes were copolymerized with styrene (M₁) in solution with radical initiation (ABCN) at 70°C. The compositions of the copolymers were calculated from nitrogen analysis and the structures were analyzed by IR, ¹H and ¹³C-NMR. The order of relative reactivity (1/r₁) for the monomers is 4-ethyl (4.69) > 3-methyl (4.18) > 4-t-butyl (2.98) > 2-ethyl (2.52) > 4-butyl (2.47) > 4-methyl (1.86) > 4-i-butyl (0.94) > 2-methyl (0.87). Decomposition of the copolymers in nitrogen occurred in two steps, first in the 200–500°C range with residue (3–8% wt), which then decomposed in the 500–800°C range.     

Novel copolymers of styrene. 1. Alkyl ring-substituted propyl 2-cyano-3-phenyl-2-propenoates

Trisubstituted ethylenes, alkyl ring-substituted propyl 2-cyano-3-phenyl-2-propenoates, RPhCH?C(CN)CO₂C₃H₇ (where R is H, 2-methyl, 3-methyl, 4-methyl, 4-ethyl, 4-propyl, 4-i-propyl, 4-butyl, 4-i-butyl, 4-t-butyl) were prepared and copolymerized with styrene. The monomers were synthesized by the piperidine catalyzed Knoevenagel condensation of ring-substituted benzaldehydes and propyl cyanoacetate, and characterized by CHN analysis, IR, ¹H and ¹³C-NMR. All the ethylenes were copolymerized with styrene (M₁) in solution with radical initiation (ABCN) at 70°C. The compositions of the copolymers were calculated from nitrogen analysis and the structures were analyzed by IR, ¹H and ¹³C-NMR. Decomposition of the copolymers in nitrogen occurred in two steps, first in the 250–500°C range with residue (2–4% wt.), which then decomposed in the 500–800°C range.     

Self-bonding in an amorphous polymer below the glass transition: A T-peel test investigation

Films of amorphous polystyrene (PS) with a weight-average molecular weight (M_w) of 225 × 10³ g/mol were bonded in a T-peel test geometry, and the fracture energy (G) of a PS/PS interface was measured at the ambient temperature as a function of the healing time (t_h) and healing temperature (T_h). G was found to develop with (t_h)^1/2 at T_h = T_g-bulk − 33 °C (where T_g-bulk is the glass-transition temperature of the bulk sample), and log G was found to develop with 1/T_h at T_g-bulk − 43 °C ≤ T_h ≤ T_g-bulk − 23 °C. The smallest measured value of G = 1.4 J/m² was at least one order of magnitude larger than the work of adhesion required to reversibly separate the PS surfaces. These three observations indicated that the development of G at the PS/PS interface in the temperature range investigated (<T_g-bulk) was controlled by the diffusion of chain segments feasible above the glass-transition temperature of the interfacial layer, in agreement with our previous findings for fracture stress development at several polymer/polymer interfaces well below T_g-bulk. Close values of G = 8–9 J/m² were measured for the symmetric interfaces of polydisperse PS [M_w = 225 × 10³, weight-average molecular weight/number-average molecular weight (M_w/M_n) = 3] and monodisperse PS (M_w = 200 × 10³, M_w/M_n = 1.04) after healing at T_h = T_g-bulk − 33 °C for 24 h. This implies that the self-bonding of high-molecular-weight PS at such relatively low temperatures is not governed by polydispersity. © 2004 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 42: 1861–1867, 2004     

Rotational diffusion of 9,10-diphenylanthracene in di-n-butyl phthalate solutions of polystyrenes by the fluorescence polarization method: Dependence on polymer concentration and molecular weight

A versatile double-beam polarization fluorimeter has been constructed for measuring the polarization of fluorescence from polymer solutions, melts, and glasses. Polarizations can be determined over a range of temperatures from ?20 to +80°C in a controlled atmosphere with a precision of ±0.001 to ±0.005 for the studies reported herein. Data collected at different temperatures for 1.5 × 10^?5M solutions of 9,10-diphenylanthracene (PA) in di-n-butyl phthalate (BP) fit a relation of the Perrin type, 1/P = (1/P₀) + (ST/_η1), where P is the polarization, T is the absolute temperature, and _η1 is the solvent viscosity. The constants P₀ and S were 0.400 ± 0.005 and (7.4 ± 0.3) × 10^?3 P/°K, respectively. Polarizations were also determined at 25.0 ± 0.1°C for BP solutions containing 1.5 × 10^?5M PA and polystyrenes at various weight fractions w₂ and molecular weights M. Rotational friction coefficients ζ_r deduced from these data showed no dependence on M from 5.1 × 10⁴ to 8.6 × 10⁵ g/mole, and a gradual increase as w₂ was varied from 0 to 0.1. It is concluded from these results that PA is an especially attractive emitter for rotational diffusion studies in nonaqueous systems, and that the abrupt changes in ζ_r with w₂ and M observed for some other emitter–polymer systems and attributed to onset of coil overlap are not universal characteristics of such systems.     

Polymerization of isobutylene by the adamantane bromide–diethylaluminum chloride catalyst system

Isobutylene has been polymerized in a continuous stirred tank reactor using a catalyst system comprised of 1-bromoadamantane and diethylaluminum chloride. The polymerization was carried out in hexane solvent at ?15 to ?27°C and gave 100% conversion to polyisobutylene (PIB) of 1000–3000 M_w. The results of pyrolysis–gas chromatography–mass spectrometry analyses are consistent with a mechanism involving the formation of the adamantyl cabocation and its addition to an isobutylene molecule to initiate polymerization. ¹³C-NMR analyses show that the PIB products contain R₂C? CR₂ and R₂C? CHR olefin types. Information on the nature of these olefins and the route to their formation has been developed.     

Synthesis,characterization and properties of a soluble polymer with a poly(phenylenevinylene) structure

Soluble poly(2,5-dialkoxy-1,4-phenylenevinylene) has been prepared via Stille coupling reaction between 2,5-dialkoxy-1,4-diiodobenzene and E-1,2-bis(tributylstannyl)-ethene in the presence of palladium complexes. Characterization of this material by means of ¹H and ¹³C nuclear magnetic resonance (NMR), ultraviolet/visible (UV/VIS) and infrared (IR) spectra is described. Molecular weights, determined by means of gelpermeation chromatography (GPC) analysis and referred to standard polystyrene, were in the range number-average molecular weights M _n = 2061–2544 and weight-average molecular weights M _w = 3347–3878. X-ray diffraction (XRD) analysis of the polymer showed semicrystalline structure. T_g = 57°C, transition to a stable smectic mesophase at 115°C and clearing point at 210°C were revealed by differential scanning calorimetry analysis, optical microscopy observation and XRD of the annealed polymer.     

Synthesis and styrene copolymerization of novel trisubstituted ethylenes: 1. Alkyl ring-substituted isopropyl 2-cyano-3-phenyl-2-propenoates

Novel trisubstituted ethylenes, alkyl ring-substituted isopropyl 2-cyano-3-phenyl-2-propenoates, RPhCH = C(CN)CO₂CH(CH₃)₂ (where R is H, 2-methyl, 3-methyl, 4-methyl, 4-ethyl, 4-propyl, 4-i-propyl, 4-butyl, 4-i-butyl, 4-t-butyl) were prepared and copolymerized with styrene. The ethylenes were synthesized by the piperidine catalyzed Knoevenagel condensation of ring-substituted benzaldehydes and isopropyl cyanoacetate, and characterized by CHN analysis, IR, ¹H and ¹³C NMR. All the ethylenes were copolymerized with styrene in solution with radical initiation (ABCN) at 70°C. The compositions of the copolymers were calculated from nitrogen analysis and the structures were analyzed by FTIR, ¹H and ¹³C NMR. Decomposition of the copolymers in nitrogen occurred in two steps, first in the 250–500°C range with residue (2-5% wt.), which then decomposed in the 500–800°C range.     

Dendritic growth of poly(ε-caprolactone) crystals from compatible blends with poly(t-butyl acrylate) at the air/water interface

Thermodynamic analyses of surface pressure-area (Π-A) isotherms and Brewster angle microscopy (BAM) reveal that poly(ε-caprolactone) (PCL) with a weight average molar mass of M_w = 10 kg mol⁻¹ and polydispersity index of M_w/M_n = 1.25 and poly(t-butyl acrylate) (PtBA, M_w = 25.7 kg mol⁻¹; M_w/M_n = 1.07) form compatible blends as Langmuir films below the dynamic collapse transition for PCL at Π = 11 mN m⁻¹. For PCL-rich blends, in situ BAM studies reveal growth of PCL crystals for compression past the PCL collapse transition. PCL crystals grown in the plateau regime of the Π-A isotherm exhibit a dendritic morphology presumably resulting from the rejection of PtBA from the growing PCL crystals and hindered diffusion of PCL from the surrounding monolayer to the crystal growth fronts. The ability to transfer the PCL dendrites as Langmuir–Schaefer films onto silicon substrates spincoated with a polystyrene layer facilitates detailed morphological characterization by optical and atomic force microscopy (AFM). AFM reveals that the dendritic branching occurs along the {100} and {110} sector boundaries and is essentially independent of composition. AFM also reveals that the average thickness of PCL dendrites formed at room temperature (22.5 °C), ∼7–8 nm, is comparable with that of PCL crystals grown from single-component PCL Langmuir films and spincoated thin films. In contrast, for PtBA-rich blend films PCL crystallization is suppressed. These findings establish PCL blends as an ideal system for exploring the interplay between chain diffusion and crystal growth in a two-dimensional confined geometry. © 2007 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 45: 3300–3318, 2007     

Living carbocationic polymerization. IV. Living polymerization of isobutylene

Truly living polymerization of isobutylene (IB) has been achieved for the first time by the use of new initiating systems comprising organic acetate-BCl₃ complexes under conventional laboratory conditions in various solvents from ?10 to ?50°C. The overall rates of polymerization are very high, which necessitated the development of the incremental monomer addition (IMA) technique to demonstrate living systems. The living nature of the polymerizations was demonstrated by linear M _n versus grams polyisobutylene (PIB) formed plots starting at the origin and horizontal number of polymer molecules formed versus amount of polymer formed plots. DP _n obeys [IB]/[CH₃COOR^t · BCl₃]. Molecular weight distributions (MWD) are very narrow in homogeneous systems (M _w/M _n = 1.2–1.3) whereas somewhat broader values are obtained when the polymer precipitates out of solution (M _w/M _n = 1.4–3.0). The MWDs tend to narrow with increasing molecular weights, i.e., with the accumulation of precipitated polymer in the reactor. Traces of moisture do not affect the outcome of living polymerizations. In the presence of monomer both first and second order chain transfer to monomer are avoided even at ?10°C. The diagnosis of first and second order chain transfer has been accomplished, and the first order process seems to dominate. Forced termination can be effected either by thermally decomposing the propagating complexes or by nucleophiles. In either case the end groups will be tertiary chlorides. The living polymerization of isobutylene initiated by ester. BCl₃ complexes most likely proceeds by a two-component group transfer polymerization.     

Thermal polycondensation of sugar fluoride to form highly branched polysaccharide

Sugar fluorides were found to undergo powder‐to‐powder polycondensation without any catalyst at 110–160 °C under vacuum, giving highly branched polysaccharides (Conv. = 40–95%, M_w = 1400–20,000). The cross‐polarized optical microscopy at 110 °C disclosed that the crystal shape of α‐glucosyl fluoride ( FGlc ) was unchanged throughout the polymerization in spite of producing the amorphous polymer ( Poly‐FGlc ). The solid‐state post polymerization of Poly‐FGlc (M_w: 2700) at 180 °C increased the higher molecular weight (M_w: 8900). The product polysaccharide was per‐O‐methylated and subjected to structure analyses. Acid‐hydrolysis, which gave a variety of the partially O‐methylated monosaccharides, suggested that the product polysaccharides had a highly branched structure consisting of all of the possible glycosidic linkages. MALDI‐TOF mass analysis revealed that the 1,6‐anhydride terminal unit was formed and participated to the polymerization. Interestingly, α‐maltosyl fluoride hydrate ( FMal·H ₂ O ) was polymerized at the lower temperature (100 °C) than the anhydrate ( FMal ), which required 160 °C for the polymerization. They produced different structure polymers even from the same monomer. The polymer from the former consisted of the disaccharide‐repeating unit, while the repeating unit of the polymer from the latter was the monosaccharide, which was formed by the acetal exchange reaction. © 2007 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 45: 3851–3860, 2007     

Synthesis of periodic copolymers via ring‐opening copolymerizations of cyclic anhydrides with tetrahydrofuran using nonafluorobutanesulfonimide as an organic catalyst and subsequent transformation to aliphatic polyesters

To synthesize polyesters and periodic copolymers catalyzed by nonafluorobutanesulfonimide (Nf₂NH), we performed ring‐opening copolymerizations of cyclic anhydrides with tetrahydrofuran (THF) at 50–120 °C. At high temperature (100–120 °C), the cyclic anhydrides, such as succinic anhydride (SAn), glutaric anhydride (GAn), phthalic anhydride (PAn), maleic anhydride (MAn), and citraconic anhydride (CAn), copolymerized with THF via ring‐opening to produce polyesters (M_n = 0.8–6.8 × 10³, M_n/M_w = 2.03–3.51). Ether units were temporarily formed during this copolymerization and subsequently, the ether units were transformed into esters by chain transfer reaction, thus giving the corresponding polyester. On the other hand, at low temperature (25–50 °C), ring‐opening copolymerizations of the cyclic anhydrides with THF produced poly(ester‐ether) (M_n = 3.4–12.1 × 10³, M_w/M_n = 1.44–2.10). NMR and matrix‐assisted laser desorption/ionization time‐of‐flight mass spectra revealed that when toluene (4 M) was used as a solvent, GAn reacted with THF (unit ratio: 1:2) to produce periodic copolymers (M_n = 5.9 × 10³, M_w/M_n = 2.10). We have also performed model reactions to delineate the mechanism by which periodic copolymers containing both ester and ether units were transformed into polyesters by raising the reaction temperature to 120 °C. © 2012 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem, 2012     

Synthesis,characterization, thermal stability,conductivity, and band gaps of substitute oligo/polyamines or polyphenol

In this study, the oxidative polycondensation reaction conditions of 3,5‐dichloroaniline (DCA), 3,4,5‐trimethoxyaniline (TMA), 3,5‐bis(trifluoromethyl)aniline (BTFMA), and 4‐{[(3,5‐dichlorophenyl)imino]methyl}phenol (DCPIMP) were studied by using NaOCl oxidant in an aqueous alkaline medium between 40 and 90°C. The structures of the synthesized monomer and polymer were confirmed by FT‐IR, Ultraviolet–visible (UV–vis), ¹H‐NMR, and ¹³C‐NMR and elemental analysis. The characterization was made by TGA–DTA, size exclusion chromatography (SEC), and solubility tests. At the optimum reaction conditions, the yields of oligo‐3,5‐dichloroaniline (ODCA), poly‐3,4,5‐trimethoxy aniline (PTMA), oligo‐3,5‐bis(trifluoromethyl)aniline (OBTFMA), and poly‐4‐{[(3,5‐dichlorophenyl) imino]methyl} phenol (PDCPIMP) were found to be 98, 48, 80, and 83% in using NaOCl oxidant. According to the SEC analysis, the number‐average molecular weight (M_n), weight‐average molecular weight (M_w) and polydispersity index (PDI) values of ODCA, PTMA, and OBTFMA were found to be 2200, 3800 g mol^?1, and 1.727; 4700, 7500 g mol^?1, and 1.596; and 1690, 1950 g mol^?1, and 1.154, respectively. According to TG analysis, the weight losses of ODCA, PTMA, OBTFMA, and PDCPIMP were found to be 78.55, 54.18, 99.38, and 59.70% at 1000°C, respectively. PTMA showed higher stability against thermal decomposition. Electrical conductivity of the polymers was measured, showing that the polymer is a typical semiconductor. The highest occupied molecular orbital (HOMO), the lowest unoccupied molecular orbital (LUMO) and electrochemical band gaps ( ) of ODCA, PTMA, OBTFMA, and PDCPIMP were calculated from their absorption edges of cyclic voltammograms. The optical band gaps (E_g) values of all compounds were calculated from UV–vis measurements. Copyright © 2009 John Wiley & Sons, Ltd.     

Synthesis and characterization of polymers and copolymers of vinylruthenocene

Homopolymers of vinylruthenocene and its copolymers with methyl acrylate, styrene, and n-vinylpyrrolidinone have been prepared by free-radical polymerization. No evidence for the electron transfer termination mechanism postulated for polymerization of vinylferrocene was observed. Yields of soluble polymers were 40–90% with M _w (4–25) × 10³ and M _w/M _n = 3.0–13.2. TGA analysis showed little weight loss up to 300°C but rapid decomposition above 300°C. Polyvinylruthenocene is a highly brittle material with T_g above 250°C. Torsional braid analysis of the copolymer samples showed T_g in the range 90–130°C which in some samples increased upon cooling and reheating. Several samples showed weak thermal transitions occurring prior to or following T_g. The rise in T_g upon cooling and reheating is indicative of possible decomposition, crosslinking, or realignment of the polymer chains.     

Synthesis and characterization of L‐leucine containing chiral vinyl monomer and its polymer,poly(2‐(methacryloyloxyamino)‐4‐methyl pentanoic acid)

A chiral monomer containing L ‐leucine as a pendant group was synthesized from methacryloyl chloride and L ‐leucine in presence of sodium hydroxide at 4 °C. The monomer was polymerized by free radical polymerization in propan‐2‐ol at 60 °C using 2,2′‐azobis isobutyronitrile (AIBN) as an initiator under nitrogen atmosphere. The polymer, poly(2‐(Methacryloyloxyamino)‐4‐methyl pentanoic acid) is thus obtained. The molecular weight of the polymer was determined to be: M_w is 6.9 × 10³ and M_n is 5.6 × 10³. The optical rotation of both chiral monomer and its polymer varies with the solvent polarity. The amplification of optical rotation due to transformation of monomer to polymer is associated with the ordered conformation of chiral monomer unit in the polymeric chain due to some secondary interactions like H‐bonding. The synthesized monomer and polymer exhibit intense Cotton effect at 220 nm. The conformation of the chain segments is sensitive to external stimuli, particularly the pH of the medium. In alkaline medium, the ordered chain conformation is destroyed resulting disordered random coils. The ordered coiling conformation is more firmly present on addition of HCl. The polymer exhibits swelling‐deswelling characteristics with the change of pH of the medium, which is reversible. The Cotton effect decreases linearly with the increase of temperature which is reversible on cooling. © 2009 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 47: 2228–2242, 2009     

Characterization of Branched Poly (vinyl Acetate) by GPC and Low Angle Laser Light Scattering Photometry

Abstract

Poly (vinyl acetate), PVAC, synthesized by bulk polymerization over a range of initiator concentrations ([AIBN] = 10^?5 to 4 × 10^?3 g-mole/1), temperatures (50°C, 60°C, 70°C, and 80°C) and conversion levels (3 to > 90%) were characterized using low angle laser light scattering (LALLS) photometry to measure M_w of the whole polymers. A number of these samples were characterized using GPC with a differential refractive index (DRI) and LALLS detector to measure the molecular weight distribution (weight fraction versus M_w). M_w for PVAC samples synthesized at suitably low initiator levels at various conversions were found to agree with classical light scattering measurements after Graessley.

An electronic device and a technique which optimizes the sensitivity and the signal-to-noise ratio of the LALLS photometer throughout the molecular weight distribution (MWD) of the GPC chromatogram were devised. These considerably simplify the operation of the LALLS for both offline and online operation with GPC.

Most importantly it was unambiguously shown that the commonly used universal calibration parameter (UCP) with GPC, [n]M_w, is incorrect for polymers with molecules having the same hydrodynamic volume but different molecular weights, i. e., those with only chain branching (LCB), copolymers with compositional drift, and polymer blends. The correct UCP was found to     

Ultrasonic Solution Degradations of Poly(Alkyl Methacrylates)

Ultrasonic (70 W, 20 kHz) solution (2%) degradations of poly(alkyl methacrylates) have been carried out in toluene at 27°C and in tetrahydrofuran (THF) at -20°C. M_w and M_n of all polymers (before and after sonification) were computed from GPC. Irrespective of the alkyl substituent, M_w decreased rapidly at first and then slowly approached limiting values. All M_w/M_n ratios were in the vicinity of 1.5 at the limiting chain lengths. For identical M_n, the rate constants k were (4.2 ± 2.0) × 10^?6 min^?1 in toluene at 27°C and (5.4 ± 2.0) × 10^?6 min^?1 in THF at -20°C. For poly(isopropyl methacrylate) and poly(octadecyl methacrylate) with higher, but identical, M_n,0, k values were higher ((9.0 ± 1.0) × 10^?6 min^?1 at 27°C and (18.0 ± 1.5) × 10^?6 min^?1 at -20°C). This suggests that M_n,0 and not the bulk size of the alkyl substituents is the factor that determines the rate of degradation. Lowering of the temperature accelerates degradation due primarily to lower chain mobility of poly-(alkyl methacrylates) and enhanced cavitation. The average number of chain scissions ([(M_n)₀/(M_n)_t] - 1) calculated from component degradation data are much higher than those obtained with overall M_n,t values.     

Eight-arm star polystyrene in methylcyclohexane: Cloud-point curves,critical lines,and coexisting densities and viscosities

We measured the cloud-point curves of eight-arm star polystyrene (sPS) in methylcyclohexane (MCH) for polymer samples of three total molecular masses [weight-average molecular weight (M_w) × 10⁻³ = 77, 215, or 268]. We found a downward shift of 5–15 K in the critical temperature (T_c) of the star polymer solutions with respect to linear polystyrene (PS) solutions of the same M_w. The shift in T_c became smaller as M_w increased. The critical volume fraction for eight-arm sPS in MCH was equal within experimental uncertainty (10–40%) to that of linear PS in MCH. For sPS of M_w = 77,000 in MCH, we studied the mass density (ρ) as a function of temperature (T). As for linear polymers in solution, the difference in ρ between coexisting phases (Δρ) could be described over t = (T_c − T)/T_c for 1.1 × 10⁻⁴ < t < 4.7 × 10⁻³ with the Ising value of the exponent β in the expression Δρ = B t^β. Both ρ(T) above T_c and the average value of ρ below T_c were linear functions of temperature; no singular corrections were observed. The measurements of the shear viscosity (η) near T_c for sPS (M_w = 74,000) in MCH indicated a strong critical anomaly in η, but the data were not precise enough for a quantitative analysis. © 2003 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 42: 129–145, 2004     

New conjugated poly(aryleneethynylenes) with main-chain photochromic units

New photochromic poly(aryleneethynylenes) have been synthesized on the basis of dibromodithienylmaleimide and bisacetylenes under the conditions of the Sonogashira reaction. Molecular masses and polydispersities of the poly(arylene ethynylenes) vary over the following ranges: M _w = 19 150–32 650, M _n = 12 000–19 200, and M _w/M _n = 1.47–1.70; the glass-transition temperatures are in the range 208–230°C; and the 10% weight-loss temperatures in air and argon are in the ranges 330–370 and 550–660°C, respectively. All poly(aryleneethynylenes) exhibit photochromic properties in both solutions and films. It has been shown that, when photochromes are incorporated into a polymer matrix, the efficiency of their photoinduced coloration diminishes, irrespective of whether they are fragments of macromolecular chains or components of polymer solutions.     

Effects of the thermal history and concentration on the aggregation of Erwinia gum in an aqueous solution

The aggregation of Erwinia (E) gum in a 0.2 M NaCl aqueous solution was investigated by multi‐angle laser light scattering and gel permeation chromatography (GPC) combined with light scattering. The GPC chromatograms of five fractions contained two peaks; the fractions had the same elution volume but different peak areas, suggesting that aggregates and single chains coexisted in the solution at 25 °C. The apparent weight‐average molecular weights (M_w) of the aggregates and single chains for each fraction were all about 2.1 × 10⁶ and 7.8 × 10⁴, respectively. This indicates that the aggregates were composed of about 27 molecules of E gum in the concentration range used (1.0 × 10⁻⁶ to 5.0 × 10⁻⁴ g/mL). The weight fraction of the aggregates (w_ag) increased with increasing concentration, but the aggregates still existed even in an extremely dilute solution. The fractionation process and polymer concentration hardly affected the apparent aggregation number but significantly changed w_ag. The E‐gum M_w decreased sharply with an increase in temperature. When the E‐gum solution was kept at 100 °C, w_ag decreased sharply for 20 h and leveled off after 100 h. Once the aggregates were decomposed at a higher temperature, no aggregation was observed in the solution at 25 °C, indicating that the aggregation was irreversible. © 2000 John Wiley & Sons, Inc. J Polym Sci B: Polym Phys 38: 1352–1358, 2000     

Amino alcohol additives for the fast living radical polymerization of methyl methacrylate with RuCl2(PPh3)3

A series of amino alcohols [e.g., R₂N (CH₂)_n OH (R = Me, Et, etc.; n = 2, 3, or 4)] were examined as additives for rate enhancement and finer reaction control in the living radical polymerization of methyl methacrylate with RuCl₂(PPh₃)₃. In general, these additives were more effective in acceleration than the corresponding amines as well as mixtures of an amine and a nonsubstituted alcohol, diamines, or diols. For example, 2-(diethylamino)ethanol significantly accelerated the polymerization (23 h, 91% at 60 °C) and gave polymers with narrower molecular weight distributions [weight-average molecular weight/number-average molecular weight (M_w/M_n) = 1.23], with respect to the system without the additive (550 h, 95%, M_w/M_n ∼ 2.0 at 80 °C; no polymerization at 60 °C). ¹H NMR analysis showed the interaction between the amino alcohols and RuCl₂(PPh₃)₃, which apparently formed a more active catalyst. Amino alcohols were also effective in Ru(Ind)Cl(PPh₃)₂-catalyzed systems (96% in 8 h at 80 °C). High-molecular-weight poly(methyl methacrylate) (M_n ∼ 1.1 × 10⁵) was synthesized with the RuCl₂(PPh₃)₃/2-(diethylamino)ethanol system, in which the polymerization reached 97% conversion in 4 h. © 2003 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 41: 3597–3605, 2003