Study of polymer complexes by size exclusion chromatography coupled with light scattering in combination with fluorescence spectroscopy

Poly(methyl methacrylate) stereocomplexes prepared at different concentration in dilute tetrahydrofuran solutions were studied by size exclusion chromatography coupled with refractive and light scattering detectors in combination with fluorescence spectroscopy. A considerable increase in segment density due to complexation compared with free poly(methyl methacrylate) chain was only slightly affected by the polymer concentration in solution where stereocomplexes were formed. At polymer concentrations up to 3×10⁻³ g cm⁻³, an increase in non‐uniformity of polymer complex molecular weight and size and a shift to higher values of both were observed. In semidilute solutions (at c > 3×10⁻³ g cm⁻³) stereocomplexes virtually did not become heavier and larger.     

Phase Separation in Aqueous Polymer Solutions as Studied by NMR Methods

Some possibilities of ¹H NMR spectroscopy in investigations of structural-dynamic changes and polymer-solvent interactions during the temperature-induced phase transitions in aqueous polymer solutions are described. Results obtained recently on D₂O solutions of poly(vinyl methyl ether) (PVME), poly(N-isopropylmethacrylamide) (PIPMAm), negatively charged copolymers of N-isopropylmethacrylamide and sodium methacrylate, and PIPMAm/PVME mixtures are discussed. A markedly different rate of dehydration process in dilute solutions on the one hand, and in semidilute and concentrated solutions on the other hand, was revealed from ¹H spin-spin relaxation measurements.     

Controlled radical polymerization of methacrylates of various structures in the presence of the AIBN-FeCl3-N,N-dimethylformamide catalytic system

The controlled radical polymerization of methyl methacrylate, 2-ethoxyethyl methacrylate, and tert-butyl methacrylate conducted via atom-transfer radical polymerization in the presence of the AIBN-FeCl₃· 6H₂O-N,N-dimethylformamide catalytic system is studied. For all the systems under study, the rate of reaction is first order with respect to the monomer concentration. The number-average molecular mass of the polymers linearly increases with conversion, and their polydispersity indexes are below 1.6. The rate of polymerization decreases in the following sequence: 2-ethoxyethyl methacrylate > methyl methacrylate > tert-butyl methacrylate. The presence of ω-terminal chlorine atoms in polymer macromolecules is confirmed by ¹H NMR spectroscopy and through the block copolymerization of methyl methacrylate with a poly(ethoxyethyl methacrylate)-based macroinitiator.     

Lithium,rubidium and cesium ion removal using potassium iron(III) hexacyanoferrate(II) supported on polymethylmethacrylate

Potassium iron(III) hexacyanoferrate(II) supported on poly methyl methacrylate, has been developed and investigated for the removal of lithium, rubidium and cesium ions. The material is capable of sorbing maximum quantities of these ions from 5.0, 2.5 and 4.5 M HNO₃ solutions respectively. Sorption studies, conducted individually for each metal ion, under optimized conditions, demonstrated that it was predominantly physisorption in the case of lithium ion while shifting to chemisorption with increasing ionic size. Distribution coefficient (K _d) values followed the order Cs⁺ > Rb⁺ > Li⁺ at low concentrations of metal ions. Following these findings Cs⁺ can preferably be removed from 1.5 to 5 M HNO₃ nuclear waste solutions.     

Ion conductivity studies of blends of poly(methyl methacrylate)-g-poly(ethylene glycol) and poly(ethylene glycol) complexed with LiCF3 SO3

Polymer electrolytes which are adhesive, transparent, and stable to atmospheric moisture have been prepared by blending poly(methyl methacrylate)-g-poly(ethylene glycol) with poly(ethylene glycol)/LiCF₃ SO₃ complexes. The maximum ionic conductivities at room temperature were measured to be in the range of 10⁻⁴ to 10⁻⁵ s cm⁻¹. The clarity of the sample was improved as the graft degree increased for all the samples studied. The graft degree of poly(methyl methacrylate)-g-poly(ethylene glycol) was found to be important for the compatibility between the poly(methyl methacrylate) segments in poly(methyl methacrylate)-g-poly(ethylene glycol) and the added poly(ethylene glycol), and consequently, for the ion conductivity of the polymer electrolyte. These properties make them promising candidates for polymer electrolytes in electrochromic devices. © 1996 John Wiley & Sons, Inc.     

New initiator system for the anionic polymerization of (meth)acrylates in toluene. IV. Random copolymerization of (meth)acrylates in toluene initiated by s-BuLi ligated by lithium silanolates

Copolymerization of binary mixtures of alkyl (meth)acrylates has been initiated in toluene by a mixed complex of lithium silanolate  (s-BuMe₂SiOLi) and s-BuLi (molar ratio > 21) formed in situ by reaction of s-BuLi with hexamethylcyclotrisiloxane (D₃). Fully acrylate and methacrylate copolymers, i.e., poly(methyl acrylate-co-n-butyl acrylate), poly(methyl methacrylate-co-ethyl methacrylate), poly(methyl methacrylate-co-n-butyl methacrylate), poly(methyl methacrylate-co-n-butyl methacrylate), poly(isobornyl methacrylate-co-n-butyl methacrylate), poly(isobornyl methacrylate-co-n-butyl methacrylate) of a rather narrow molecular weight distribution have been synthesized. However, copolymerization of alkyl acrylate and methyl methacrylate pairs has completely failed, leading to the selective formation of homopoly(acrylate). As result of the isotactic stereoregulation of the alkyl methacrylate polymerization by the s-BuLi/s-BuMe₂SiOLi initiator, highly isotactic random and block copolymers of (alkyl) methacrylates have been prepared and their thermal behavior analyzed. The structure of isotactic poly(ethyl methacrylate-co-methyl methacrylate) copolymers has been analyzed in more detail by Nuclear Magnetic Resonance (NMR). © 1999 John Wiley & Sons, Inc. J Polym Sci A: Polym Chem 37: 2525–2535, 1999     

Activation of stable polymeric esters by using organo‐activated acyl transfer reactions

In this study, we succeeded in the in situ activation of nonactivated ester moieties embedded in polymer structures. Although poly(pentafluorophenyl methacrylate) (PPFPMA) can react with 2‐ethylhexylamine at 50 °C in the presence of proton scavenger such as NEt₃, such conditions were not suitable for poly(phenyl methacrylate) (PPhMA). Nevertheless, the combination of organo‐activating agents, namely 1,8‐diazabicyclo[5.4.0]undec‐7‐ene (DBU) and 1,2,4‐triazole (TZ) led to a facile conversion from ester to amide for PPhMA. The reaction between PPhMA and 2‐ethylhexylamine was conducted at 120 °C in the presence of one equivalent of TZ and three equivalents of DBU and yielded >99% ester conversion to afford corresponding polymethacrylamide derivatives as confirmed by FT‐IR and ¹H NMR measurements. In addition, poly(2,2,2‐trifluoroethyl methacrylate) (PTFEMA) and poly(methyl methacrylate) (PMMA) were also allowed to react with amines in the presence of the organo‐activating agents with dramatically increased conversions (>70%). © 2014 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2014 , 52, 1353–1358     

1H NMR relaxation study of polymer-solvent interactions during thermotropic phase transition in aqueous solutions

The dynamic-structural changes and polymer - solvent interactions during the thermotropic phase transition in poly(vinyl methyl ether) (PVME)/D₂O solutions in a broad range of polymer concentrations (c = 0.1-60 wt.-%) were studied combining the measurements of ¹H NMR spectra, spin-spin (T₂) and spin-lattice (T₁) relaxation times. Phase separation in solutions results in a marked line broadening of a major part of polymer segments, evidently due to the formation of compact globular-like structures. The minority (∼15%) mobile component, which does not participate in the phase separation, consists of low-molecular-weight fractions of PVME, as shown by GPC. Measurements of spin-spin relaxation times T₂ of PVME methylene protons have shown that globular structures are more compact in dilute solutions in comparison with semidilute solutions where globules probably contain a certain amount of water. A certain portion of water molecules bound at elevated temperatures to (in) PVME globular structures in semidilute and concentrated solutions was revealed from measurements of spin-spin and spin-lattice relaxation times of residual HDO molecules.     

Incorporation of nonionic emulsifier inside methacrylic polymer particles in emulsion polymerization

The incorporations of polyoxyethylene lauryl ether (Emulgen 109P) and polyoxyethylene nonylphenyl ether (Emulgen 911) nonionic emulsifiers inside poly(methyl methacrylate) (PMMA), poly(ethyl methacrylate) (PEMA), and poly(iso-butyl methacrylate) (Pi-BMA) particles prepared by emulsifier-present emulsion polymerizations were examined. To measure the amounts of the incorporated nonionic emulsifiers, optimum compositions of 2-propanol aqueous solutions to remove the nonionic emulsifier from the particle surfaces without removal from the insides were determined. The amount of the incorporation measured by gel permeation chromatography was increased in the order of PMMA > PEMA > Pi-BMA, which accorded with the order of miscibility between each polymer and the emulsifier.     

A cationic bridged zirconocene complex as the catalyst for the stereospecific polymerization of methyl methacrylate

The cationic bridged zirconocene complex [iPr(Cp)(Ind)Zr(Me)(THF)][BPh₄] ( 1 ‐BPh₄) was synthesized. Polymerization of methyl methacrylate with 1 ‐BPh₄ in CH₂Cl₂ at temperatures between –20 and 20°C led to the formation of isotactic poly(methyl methacrylate). The low polydispersity index of the polymer obtained and a successful two step polymerization of methyl methacrylate with 1 ‐BPh₄ are hints towards a living polymerization mechanism. ¹H and ¹³C NMR analysis revealed an enantiomorphic site‐controlled mechanism for the formation of isotactic poly(methyl methacrylate).     

Spectral and chemical monitoring of cyclo-addition reaction of CO2 with poly(MMA-co-GMA) copolymers

This paper deals with the monitoring cyclo-addition of CO₂ to methyl methacrylate（MMA）-glycidyl methacrylate （GMA） copolymers using spectral（¹H-NMR and FTIR） and chemical（elemental analysis and titration） methods.Thus, poly（MMA-co-GMA）,was first prepared via solution polymerization.The copolymer was then treated with CO₂ gas flow in the presence of cetyltrimethyl ammoniumbromide as a catalyst.In terms of the carbonation reaction time,the terpolymer poly（MMA-co-GMA-co-2-oxo-l,3-dioxolane-4-yl-methyl methacrylate） was prepared in various yield of CO₂ fixation （>90%）.The peak intensity changes in the ¹H-NMR and FTIR spectra provided excellent demonstrative techniques to monitor the carbonation reaction progression.In a comparative analytical viewpoint,the NMR and elemental analysis were recognized to be the most accurate ways to follow the cyclo-addition reaction progression.However,titration was recognized to be the most preferred method,because it is a very inexpensive,facile and available method with a reasonable costaccuracy balance.     

Rare‐earth‐metal‐initiated polymerizations of (meth)acrylates and block copolymerizations of olefins with polar monomers

The organo‐rare‐earth‐metal‐initiated living polymerization of methyl methacrylate (MMA) was first discovered in 1992 with (C₅Me₅)₂LnR (where R is H or Me and Ln is Sm, Yb, Y, or La) as an initiator. These polymerizations provided highly syndiotactic (>96%) poly(methyl methacrylate) (PMMA) with a high number‐average molecular weight (M_n > 1000 × 10³) and a very narrow molecular weight distribution [weight‐average molecular weight/number‐average molecular weight (M_w/M_n) < 1.04] quantitatively in a short period. Bridged rare‐earth‐metallocene derivatives were used to perform the block copolymerization of ethylene or 1‐hexene with MMA, methyl acrylate, cyclic carbonate, or ?‐caprolactone in a voluntary ratio. Highly isotactic (97%), monodisperse, high molecular weight (M_n > 500 × 10³, M_w/M_n < 1.1) PMMA was first obtained in 1998 with [(Me₃Si)₃C]₂Yb. Stereocomplexes prepared by the mixing of the resulting syndiotactic and isotactic PMMA revealed improved physical properties. © 2001 John Wiley & Sons, Inc. J Polym Sci Part A: Polym Chem 39: 1955–1959, 2001     

ESR Study of Stable N,N,N",N"-Tetramethyl-4,4"-diaminodiphenylmethane Radicals in Solid Solutions

The ESR spectra of -irradiated N,N,N",N"-tetramethyl-4,4"-diaminodiphenylmethane (Am) in solid solutions of poly(vinyl chloride), poly(methyl methacrylate), and benzene were studied. The formation mechanism of the free radical Am^·in these solutions was discussed. Along with Am^·, the formation of radicals with the cyclohexadienyl structure was shown to be possible in Am irradiation. The influence of the matrix structure on the radiation-chemical yield of Am^·radicals and their thermal stability was established. The radiation-induced chemical transformations of free radicals and transient ionic species resulting in the formation of terminal alkyl radicals in poly(methyl methacrylate) were investigated. Data on the mechanism of the protective action of the Am additive during PMMA radiolysis were obtained.     

Synthesis and micelle formation of triblock copolymers of poly(methyl methacrylate)-b-poly(ethylene oxide)-b-poly(methyl methacrylate) in aqueous solution

Amphiphilic triblock copolymers of poly(methyl methacrylate)-b-poly(ethylene oxide)-b-poly(methyl methacrylate) (PMMA-b-PEO-b-PMMA) with well-defined structure were synthesized via atom transfer radical polymerization (ATRP) of methyl methacrylate (MMA) initiated by the PEO macroinitiator. The macroinitiator and triblock copolymer with different PMMA and/or PEO block lengths were characterized with ¹H and ¹³C NMR and gel permeation chromatography (GPC). The micelle formed by these triblock copolymers in aqueous solutions was detected by fluorescence excitation and emission spectra of pyrene probe. The critical micelle concentration (CMC) ranged from 0.0019 to 0.016 mg/mL and increased with increasing PMMA block length, while the PEO block length had less effect on the CMC. The partition constant K_v for pyrene in the micelle and in aqueous solution was about 10⁵. The triblock copolymer appeared to form the micelles with hydrophobic PMMA core and hydrophilic PEO loop chain corona. The hydrodynamic radius R_h,app of the micelle measured with dynamic light scattering (DLS) ranged from 17.3 to 24.0 nm and increased with increasing PEO block length to form thicker corona. The spherical shape of the micelle of the triblock copolymers was observed with an atomic force microscope (AFM). Increasing hydrophobic PMMA block length effectively promoted the micelle formation in aqueous solutions, but the micelles were stable even only with short PMMA blocks.     

ATRP of MMA under 60Co γ‐irradiation at room temperature

In this work, atom transfer radical polymerization (ATRP) of methyl methacrylate (MMA) was successfully carried out at room temperature (25 °C) under ⁶⁰Co γ‐irradiation environment. The polymerization proceeded smoothly with high conversion (>90%) within 7 h. The polymerizations kept the features of controlled radical polymerization: first‐order kinetics, well‐predetermined number‐average molecular weights (M_n,GPC), and narrow molecular weight distributions (M_w/M_n < 1.25). ¹H NMR spectroscope and matrix‐assisted laser desorption/ionization time‐of‐flight mass spectrometry confirmed that poly(methyl methacrylate) (PMMA) chain was end‐capped by the initiator moieties. The Cu(II) concentration could reduce to 20 ppm level while keeping good control over molecular weights. This is the first successful example for the ATRP of MMA under ⁶⁰Co γ‐irradiation at room temperature. © 2011 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem, 2011     

Synthesis of ABABA pentablock copolymers via copper mediated living radical polymerisation

In this work, the syntheses of poly(butyl methacrylate-b-methyl methacrylate-b-butyl methacrylate) triblock copolymer and poly(methyl methacrylate-b-butyl methacrylate-b-methyl methacrylate-b-butyl methacrylate-b-methyl methacrylate) pentablock copolymers using copper mediated living radical polymerisation are reported. Living radical polymerisations were performed using the system Cu^IBr/N-(n-propyl)-2-pyridylmethanimine as catalyst in conjunction with a difunctional initiator, the 1,4-(2^′-bromo-2^′-methylpropionoto)benzene (1). The syntheses of poly(MMA), poly(BMA-b-MMA-b-BMA) and poly(MMA-b-BMA-b-MMA-b-BMA-b-MMA) are described in detail using ¹H NMR spectroscopy and size exclusion chromatography. The living behaviour and the blocking efficiency of these polymerisations were investigated in each case. Difunctional initiator, 1, based on hydroquinone was synthesised and fully characterised and subsequently used to give difunctional poly(methyl methacrylate) macroinitiators with molecular weights up to 54,000 g mol⁻¹ and polydispersity between 1.07 and 1.32; molecular weights were close to the theoretical values. The difunctional macroinitiators were used to reinitiate butyl methacrylate to give triblock copolymers of M_n between 17,500 and 45,700 g mol⁻¹. Polydispersities remained narrow below 25,000 g mol⁻¹ but broadened at higher masses. The difunctional triblock macroinitiators were subsequently used to reinitiate methyl methacrylate to give ABABA pentablock copolymers with M_n up to 37,000 g mol⁻¹ with polydispersity=1.13. Under certain conditions radical-radical reaction led to a broadening of polydispersity index.     

Fluorescence Properties of Europium and Terbium Triundecylenate-Containing Polymers and Solutions

Europium triundecylenate, Eu(UA)₃, and terbium triundecylenate, Tb(UA)₃, were prepared by the method described in our previous paper. Either Eu(UA)₃ or Tb(UA)₃ was dissolved in methacrylic acid (<20%) and copolymerized as a crosslinker with methyl methacrylate (>80) by bulk polymerization in molds made of two glass plates. The fluorescence spectroscopy of these Eu- or Tb-containing polymers under ultraviolet/visible excitation light was investigated. The fluorescence spectroscopy of solutions of Eu(UA)₃ or Tb(UA)₃ in methacrylic acid was measured and compared with that of the solid-state Eu- or Tb-containing polymers. The fluorescence excitation and emission spectra of the solutions and polymers showed the characteristic features of free Eu³⁺ or Tb³⁺. The lifetime fluorescence of the solutions and polymers with Eu³⁺ are also included.     

Effects of Ionic Liquid [Me3NC2H4OH]+[ZnCl3]− on γ‐Radiation Polymerization of Methyl Methacrylate in Ethanol and N,N‐Dimethylformamide

Summary: Radiation‐induced polymerization of methyl methacrylate (MMA) in ethanol (EtOH) and N,N‐dimethylformamide (DMF) in the presence of ionic liquid [Me₃NC₂H₄OH]⁺[ZnCl₃]⁻ is reported. A substantial increase in monomer conversion and molecular weight is observed at room‐temperature ionic liquid (RTIL) >60 vol.‐%, and the resulting PMMA has a broad multimodal MWD. A clear difference in the MWD pattern is noted between EtOH/RTIL and DMF/RTIL systems, probably due to the complicated interactions between the solvent and ionic liquid.

Gel permeation chromatography traces of poly(methyl methacrylate) obtained by radiation polymerization in EtOH/RTIL and DMF/RTIL mixed solvent. Organic/RTIL (v/v): 1) 100:0; 2) 80:20; 3) 60:40; 4); 40:60; 5) 0:100.     

Characterization and degradation of the poly(methylphenylsiloxane)–poly(methyl methacrylate) graft copolymer

Poly(methylphenylsiloxane)–poly(methyl methacrylate) graft copolymers (PSXE-g-PMMA) were prepared by condensation reaction of poly(methylphenylsiloxane)-containing epoxy resin (PSXE) with carboxyl-terminated poly(methyl methacrylate) (PMMA), and they were characterized by gel permeation chromatography (GPC), infrared (IR), and ²⁹Si and ¹³C nuclear magnetic resonance (NMR). The microstructure of the PSXE-g-PMMA graft copolymer was investigated by proton spin–spin relaxation T₂ measurements. The thermal stability and apparent activation energy for thermal degradation of these copolymers were studied by thermogravimetry and compared with unmodified PMMA. The incorporation of poly(methylphenylsiloxane) segments in graft copolymers improved thermal stability of PMMA and enhanced the activation energy for thermal degradation of PMMA. © 1998 John Wiley & Sons, Inc. J. Polym. Sci. A Polym. Chem. 36: 2521–2530, 1998     

Synthesis of core/shell structure of glycidyl–functionalized poly(methyl methacrylate) latex nanoparticles via differential microemulsion polymerization

The differential microemulsion polymerization technique was used to synthesize the nanoparticles of glycidyl-functionalized poly(methyl methacrylate) or PMMA via a two-step process, by which the amount of sodium dodecyl sulfate (SDS) surfactant required was 1/217 of the monomer amount by weight and the surfactant/water ratio could be as low as 1/600. These surfactant levels are extremely low in comparison with those used in a conventional microemulsion polymerization system. The glycidyl-functionalized PMMA nanoparticles are composed of nanosized cores of high molecular weight PMMA and nano-thin shells of the random copolymer poly[(methyl methacrylate)-ran-(glycidyl methacrylate)]. The particle sizes were about 50 nm. The ratios of the glycidyl methacrylate in the glycidyl-functionalized PMMA were achieved at about 5–26 wt.%, depending on the reaction conditions. The molecular weight of glycidyl-functionalized PMMA was in the range of about 1 × 10⁶ to 3 × 10⁶ g mol⁻¹. The solid content of glycidyl-functionalized PMMA increased when the amount of added glycidyl methacrylate was increased. The glycidyl-functionalized polymer on the surface of nano-seed PMMA nanoparticles was a random copolymer which was confirmed by ¹H-NMR spectroscopy. The amounts of functionalization were investigated by the titration of the glycidyl functional group. The structure of the glycidyl-functionalized PMMA nanoparticles was investigated by means of TEM. The glycidyl-functionalized PMMA has two regions of T_g which are at around 90 °C and 125 °C, respectively, of which the first one was attributed to the poly[(methyl methacrylate)-ran-(glycidyl methacrylate)] and the second one was due to the PMMA. A core/shell structure of the glycidyl-functionalized PMMA latex nanoparticles was observed.