Thermal degradation of bromine-containing polymers: Part 10—Copolymers of 2,3-dibromopropyl methacrylate and 2,3-dibromopropyl acrylate with methyl acrylate

The products of the thermal degradation of copolymers of methyl acrylate (MA) with 2,3-dibromopropyl methacrylate (2,3-DBPM) and 2,3-dibromopropyl acrylate (2,3-DBPA) have been analysed quantitatively using thermal analysis, infra-red spectroscopy, mass spectrometry and gas-liquid chromatography. The dominant products from the first of these systems are 2,3-DBPM monomer and chain fragments reflecting the behaviours of the homopolymers of 2,3-DBPM and MA, respectively. The yield of methyl bromide is at a maximum when the proportion of interunit bonds between the two monomers is at a maximum. From the second system, the dominant products are methyl bromide and the chain fragment or cold ring fraction. The mechanisms by which these and the many other products are formed are discussed with reference to related systems which have been studied previously.     

Thermal degradation of bromine-containing polymers. Part 9—Copolymers of 2,3-dibromopropyl methacrylate and 2,3-dibromopropyl acrylate with styrene

The products of the thermal degradation of copolymers of styrene (S) with 2,3-dibromopropyl methacrylate (2,3-DBPM) and 2,3-dibromopropyl acrylate (2,3-DBPA) have been analysed quantitatively using thermal analysis, infra-red spectroscopy, mass spectrometry and gas-liquid chromatography. The products are generally similar to those which result from the degradation of the two homopolymers and no significant interaction occurs between the two types of units in the polymer chains. The only abnormal feature is the fact that the yield of 2,3-DBPA increases as the 2,3-DBPA content of copolymers of 2,3-DBPA and S decreases but this is consistent with previous observations in related copolymer systems.     

Phase behavior and modeling of the poly(methyl methacrylate)–CO2–methyl methacrylate system

Cloud-point data for the system poly(methyl methacrylate) (PMMA)–CO₂–methyl methacrylate (MMA) are measured in the temperature range of 26 to 170°C, to pressures as high as 2500 bar, and with cosolvent concentrations of 10.4, 28.9, and 48.4 wt.%. PMMA does not dissolve in pure CO₂ to 255°C and 2550 bar. The cloud-point curve for the PMMA–CO₂–10.4 wt.% MMA system exhibits a negative slope that reaches 2500 bar at 105°C. With 28.9 wt.% MMA the cloud-point curve remains relatively flat at ∼900 bar for temperatures between 25 and 170°C. With 48.4 wt.% MMA the cloud-point curve exhibits a positive slope that extends to 20°C and ∼100 bar. Pressure-composition isotherms are also reported for the CO₂–MMA system at 40.0, 80.0, 105.5°C. This system exhibits type-I phase behavior with a continuous mixture–critical curve. The Peng–Robinson (PR) and SAFT equations of state model the CO₂–MMA data reasonably well without any binary interaction parameters, although the PR equation provides a better representation of the mixture-critical region. It is not possible to obtain even a qualitative fit of the PMMA–MMA–CO₂ data with the SAFT equation of state. The SAFT model qualitatively shows that the cloud-point pressure decreases with increasing MMA concentration and that the cloud-point curve exhibits a positive slope for very high concentrations of MMA in solution.     

Preparation and characterization of blended solid polymer electrolyte 49% poly(methyl methacrylate)-grafted natural rubber:poly(methyl methacrylate)–lithium tetrafluoroborate

The preparation and characterization of blended solid polymer electrolyte 49% poly(methyl methacrylate)-grafted natural rubber (MG49):poly(methyl methacrylate) (PMMA) (30:70) were carried out. The effect of lithium tetrafluoroborate (LiBF₄) concentration on the chemical interaction, structure, morphology, and room temperature conductivity of the electrolyte were investigated. The electrolyte samples with various weight percentages (wt.%) of LiBF₄ salt were prepared by solution casting technique and characterized by Fourier transform infrared spectroscopy, X-ray diffraction (XRD), scanning electron microscopy (SEM), and electrochemical impedance spectroscopy. Infrared analysis demonstrated that the interaction between lithium ions and oxygen atoms occurred at symmetrical stretching of carbonyl (C=O) (1,735 cm^?1) and asymmetric deformation of (O–CH₃) (1,456 cm^?1) via the formation of coordinate bond on MMA structure in MG49 and PMMA. The reduction of MMA peaks intensity at the diffraction angle, 2θ of 29.5° and 39.5° was due to the increase in weight percent of LiBF₄. The complexation occurred between the salt and polymer host had been confirmed by the XRD analysis. The semi-crystalline phase of polymer host was found to reduce with the increase in salt content and confirmed by XRD analysis. Morphological studies by SEM showed that MG49 blended with PMMA was compatible. The addition of salt into the blend has changed the topological order of the polymer host from dark surface to brighter surface. The SEM analyses supported the enhancement of conductivity with the addition of salt. The conductivity increased drastically from 2.0 to 3.4?×?10^?5 S cm^?1 with the addition of 25 wt.% of salt. The increase in the conductivity was due to the increasing of the number of charge carriers in the electrolyte. The conductivity obeys Arrhenius equation in higher temperature region from 333 to 373 K with the pre-exponential factor σ _o of 1.21?×?10^?7 S cm^?1 and the activation energy E _a of 0.46 eV. The conductivity is not Arrhenian in lower temperature region from 303 to 323 K.     

Molecular simulation of an amorphous poly(methyl methacrylate)–poly(tetrafluoroethylene) interface

Molecular dynamics calculations of an amorphous interfacial system of poly(methyl methacrylate) (PMMA) and poly(tetrafluoroethylene) (PTFE) containing about 10,000 interaction sites were performed for 15 ns under constant pressure and constant temperature conditions. The time evolutions of the thickness, density and number of atomic pairs in the interfaces suggested that the interfaces reached their equilibrium states with an interfacial thickness of about 2 nm at 500 K. The molecular motion in the interface and bulk was compared using mean square displacement and torsional autocorrelation function. The separation at a PMMA/PTFE interface was mimicked using non-equilibrium molecular dynamics calculations by applying the potential energy to the MD cell in a direction perpendicular to the interface. Initially, the PTFE layer close to the interface was deformed, and before complete separation, some segments of the PTFE molecules extended from the bulk to the surface of the PMMA layer, which were attached by the intermolecular interaction. The remaining PTFE molecules were entangled in the bulk, which probably prevented the transfer of the PTFE molecules to the surfaces of the PMMA layers. On the other hand, the PMMA layer was only slightly deformed. This separation behavior can be explained by taking into account the intermolecular interaction, the barrier to the conformational changes of the backbones and the entanglement of the PTFE molecules in the bulk.     

Optical properties of polymer blends composed of poly(methyl methacrylate) and ethylene–vinyl acetate copolymer

Optical properties for immiscible polymer blends composed of poly(methyl methacrylate), PMMA, and ethylene–vinyl acetate copolymer (EVA) are studied employing various EVA samples with different vinyl acetate contents. PMMA/EVA shows transparency at room temperature when the difference in refractive index between both phases is small. The light transmittance, however, decreases with increasing the ambient temperature. This phenomenon is attributed to the difference in the volume expansion ratio, leading to the difference in refractive index, between PMMA and EVA. It is found that addition of tricresyl phosphate, TCP, improves the transparency and its temperature dependence. As a result, a ternary PMMA/EVA/TCP blend shows high level of transparency in the wide temperature range, although it has apparent phase separated morphology.     

Photoinduced excimer formation of boron difluoride β-diketonates in poly(methyl methacrylate)

Russian Chemical Bulletin - The photochemical behavior of β-diketonates of boron difluoride in poly(methyl methacrylate) was studied. Excimers of boron chelates are formed in the course of UV...     

Synthesis and Characterization of Poly(methyl methacrylate‐co‐hydroxyethyl methacrylate)‐b‐polyisobutylene‐b‐poly(methyl methacrylate‐co‐hydroxyethyl Methacrylate) Triblock Copolymers

The synthesis of poly[(methyl methacrylate‐co‐hydroxyethyl methacrylate)‐b‐isobutylene‐b‐(methyl methacrylate‐co‐hydroxyethyl methacrylate)] P(MMA‐co‐HEMA)‐b‐PIB‐b‐P(MMA‐co‐HEMA) triblock copolymers with different HEMA/MMA ratios has been accomplished by the combination of living cationic and anionic polymerizations. P(MMA‐co‐HEMA)‐b‐PIB‐b‐P(MMA‐co‐HEMA) triblock copolymers with different compositions were prepared by a synthetic methodology involving the transformation from living cationic to anionic polymerization. First, 1,1‐diphenylethylene end‐functionalized PIB (DPE‐PIB‐DPE) was prepared by the reaction of living difunctional PIB and 1,4‐bis(1‐phenylethenyl)benzene (PDDPE), followed by the methylation of the resulting diphenyl carbenium ion with dimethylzinc (Zn(CH₃)₂). The DPE ends were quantitatively metalated with n‐butyllithium in tetrahydrofuran, and the resulting macroanion initiated the polymerization of methacrylates yielding triblock copolymers with high blocking efficiency. Microphase separation of the thus prepared triblock copolymers was evidenced by the two glass transitions at ?64 and +120°C observed by differential scanning calorimetry. These new block copolymers exhibit typical stress‐strain behavior of thermoplastic elastomers. Surface characterization of the samples was accomplished by angle‐resolved X‐ray photoelectron spectroscopy (XPS), which revealed that the surface is richer in PIB compared to the bulk. However, a substantial amount of P(MMA‐co‐HEMA) remains at the surface. The presence of hydroxyl functionality at the surface provides an opportunity for further modification.     

Interpenetrating polymer networks from castor oil based polyurethanes and poly(methyl acrylate)—IV

Castor oil and toluene-2,4-diisocyanate were reacted to form liquid prepolyurethane under various experimental conditions, varying the NCO/OH ratio. The prepolyurethanes (PPU) thus obtained were interpenetrated with methylacrylate monomer containing ethylene glycol dimethacrylate, using radical polymerization initiated by benzoyl peroxide. The PPU/MA interpenetrating polymer networks were obtained as transparent tough films by transfer moulding. They were characterized by resistance to chemical reagents, thermal behaviour and mechanical properties. The mechanothermal behaviour was studied by dynamic mechanical analysis. The morphology was examined by Scanning Electron Microscopy. Dielectric properties were studied.     

Formation and structure of chitosan–poly(sodium methacrylate) complex nanoparticles

Interpolyelectrolyte complex (IPEC) dispersions were prepared from chitosan and poly(sodium acrylate), NaPMA, by mixing their solutions, at different carboxyl-to-aminium molar ratios, r_CA. Gyration radius was determined by small angle x-ray scattering (SAXS) and showed that, as r_CA was increased, IPEC dimensions decreased and reached a minimum at r_CA?=?0.75, which was considered the ratio at which IPEC cluster dimensions were minimum, following collapse, phase segregation, nucleation, and growth of larger particles. Pair distance distributions, P(r), became narrower up to r_CA?=?0.75, increasing its width from this point. Relaxation-related parameters from dynamic light scattering (DLS) intensity correlation functions (ICFs) identified three main relaxation processes. The fast process, related to free polyelectrolyte molecules random motion disappeared as r_CA, was increased. The other two relaxation processes also were a function of r_CA and presented marked changes at r_CA?=?0.75. At the same value of r_CA, the energy of activation for the average relaxation rate showed the occurrence of a clear change in the nature of IPEC-related interactions. As hydrodynamic diameter, determined by DLS, was much larger than the gyration radius determined by SAXS, IPEC particles could be described as being composed by a core, rich in segregated, insoluble material, enveloped by IPEC soluble clusters, possibly in the form of water-rich gels.     

Pyrolysis mass spectrometry analysis of poly(vinyl acetate), poly(methyl methacrylate) and their blend coalesced from inclusion compounds formed with γ-cyclodextrin

Direct insertion probe pyrolysis mass spectrometry (DIP-MS) analyses of poly(methyl methacrylate) (PMMA), poly(vinyl acetate) (PVAc) and binary PMMA/PVAc guests, coalesced from their inclusion compounds (ICs) formed with host γ-cyclodextrin (γ-CD) through removal of the γ-CD host, have been performed. A slight increase in the thermal stabilities of the coalesced polymers were recorded both by TGA and DIP-MS compared to the corresponding as-received polymers. The DIP-MS observations pointed out that the thermal stability and degradation products of these polymers are affected once they are included inside the IC channels created by the stacked host γ-CDs. DIP-MS observations suggested that the degradation mechanisms for PMMA and PVAc chains in their coalesced blend were significantly altered from those observed in their as-received and solution blended samples. This was attributed to the presence of specific molecular interactions between the intimately mixed PMMA and PVAc chains in their coalesced blend.     

Surface structure of thin film blends of polystyrene and poly(n -butyl methacrylate)

 Thin films of blends of polystyrene (PS) and poly(n-butyl methacrylate) (PBMA) were prepared by spin-casting onto silicon wafers in order to map the lateral distribution of the two polymers. The surfaces were examined by atomic force microscopy (AFM) secondary ion mass spectroscopy X-ray photoelectron spectroscopy (XPS) and photoemission electron microscopy (PEEM). Films with PBMA contents of 50% w/w or less were relatively smooth, but further increase in the PBMA content produced, initially, protruding PS ribbons and then, for PBMA ≥80% w/w, isolated PS islands. At all concentrations the topmost surface (0.5–1.0 nm) was covered by PBMA, whilst the PBMA concentration in the near-surface region, measured by XPS, increased with bulk content to eventual saturation. PEEM measurements of a PS–PBMA film at the composition at which ribbon features were observed by AFM also showed a PS-rich ribbon structure surrounded by a sea of mainly PBMA. Received: 6 December 1999/Accepted: 5 April 2000     

The determination of the Förster distance (R0) for phenanthrene and anthracene derivatives in poly(methyl methacrylate) films

Experiments that employ direct resonance energy transfer (DET) to obtain information about distances or domain sizes in polymer systems require independent information about the magnitude of the characteristic (F?rster) energy transfer distance R(0). Values of R(0) are relatively straightforward to obtain by the traditional spectral overlap method (R(0)(SO)) for dyes in fluid solution, but are much more difficult to obtain for dyes in rigid polymer films. Here one can obtain a value for R(0) as a fitting parameter (R(0)(FF)) for donor fluorescence decay experiments for samples containing a random distribution of donor and acceptor dyes in the polymer film. In previous experiments from our group, we needed values of R(0) for various phenanthrene (Phe, donor) and anthracene (An, acceptor) derivatives. In this paper, we describe experiments which determine R(0) values by both methods for a series of Phe-An donor-acceptor pairs in poly(methyl methacrylate) and polystyrene films. Both the location of substituents on the donor and acceptor as well as the choice of the medium had an effect on the measured R(0), which varied between 2.0 and 2.6 nm. We also ascertained that there is some unknown factor, also prevalent in the work of others, which results in the F?rster radius being larger when determined by the F?rster fit method than by the method of spectral overlap.     

The ATRP Synthesis of the Potential Thermoplastic Elastomer Poly(methyl methacrylate)–b-(lauryl methacrylate)-b-(methyl methacrylate) Hitherto Unrealized by Ionic Polymerization

The triblock copolymer poly(methyl methacrylate-b-lauryl methacrylate-b-methyl methacrylate) {P(MMA-b-LMA-b-MMA)} has been synthesized by a two stage atom transfer radical polymerization in bulk at near room temperature (ca. 35 °C) using CuCl/pentamethyldiethylenetriamine (PMDETA)/tricaprylylmethylammonium chloride (Aliquat®336) complex as the catalyst and 1,2-bis (bromoisobutyryloxy)ethane (BIBE) as the initiator for the polymerization of LMA in the first stage. The same catalyst was also used for the polymerization of MMA in the second stage. The dynamic mechanical thermal analysis of a sample with the middle block M_n = 82000 and each end block M_n = 14500 showed typical features of a thermoplastic elastomer.     

Selective sorption of atactic poly(methyl methacrylate) in polar binary mixtures—8. Chloroform-butyl acetate

We report the behaviour of PMMA in the polar binary mixture chloroform-butyl acetate at 298 K. Mark-Houwink-Sakurada constants, second virial coefficients, unperturbed dimensions and preferential sorption coefficients have been determined for this system at 298 K using viscometry and laser light scattering. No inversion in solvation was found; chloroform is preferentially adsorbed on PMMA over the whole composition range. Viscometric measurements suggest the possible existence of a complex between chloroform and butyl acetate; this complex may participate in the solvation phenomena.     

Synthesis of a novel centipede-like copolymer of styrene and methyl methacrylate

A well-defined,A2B-type,centipede-like copolymer of styrene and methyl methacrylate(PS-PS-PMMA) was synthesized by the combination of living anionic polymerization and atom transfer radical polym-erization(ATRP) . The synthetic approach involves the coupling reaction of polystyrene(PS) backbone bearing 1,1-diphenylethene(DPE) pendant groups,produced by ATRP and Wittig reaction,with living polystyryllithium(PSLi) ,and subsequent polymerization of the resulting 1,1-diphenylmethyl anions with methy methacrylate. The centipede-like copolymer was characterized by 1H NMR,IR,SEC,SLS,and DSC measurements.     

Thermal properties of the γ-Fe2O3/poly(methyl methacrylate) core/shell nanoparticles

Thermal properties of γ-Fe₂O₃/poly(methyl methacrylate) (PMMA) core/shell particles with an average core size of 4 nm were studied through measurements of thermogravimetry, powder X-ray diffraction and magnetization. The thermal degradation of the PMMA shell in the air was found to occur at temperatures lower by about 60 °C than that of free PMMA. Random scission of the PMMA chains seemed to be catalyzed by the core oxide. The γ-Fe₂O₃ to α-Fe₂O₃ structural transformation took place at different temperatures depending upon the shell material. Namely, α-Fe₂O₃ was the only product for the caprylate-capped γ-Fe₂O₃ nanoparticles treated at 400 °C, whereas γ-Fe₂O₃ still remained for the γ-Fe₂O₃/PMMA composite treated at 500 °C. It is possible that some species containing silicon of the polymerization initiator origin were formed on the surface and prevented interparticle atomic diffusions needed for the γ–α transformation.     

Influence of α-Fe2O3 nanorods on the thermal stability of poly(methyl methacrylate) synthesized by in situ bulk polymerisation of methyl methacrylate

α-Fe₂O₃ nanorods were incorporated into poly(methyl methacrylate) (PMMA) by in situ radical polymerisation of methyl methacrylate initiated by 2,2′-azobisisobutyronitrile. The α-Fe₂O₃ nanorods were synthesized by forced hydrolysis of FeCl₃ and structural characterization was performed by X-ray diffraction and transmission electron microscopy. The molar mass and the polydispersity index of synthesized PMMA samples were determined by gel permeation chromatography. The content of residual monomer was determined by ¹H NMR spectroscopy. The influence of α-Fe₂O₃ nanorods on the thermal stability of the polymer was investigated using thermogravimetry and differential scanning calorimetry. The molar mass and polydispersity index of PMMA were dependent on the content of α-Fe₂O₃ nanorods. The values of the glass transition temperature of the nanocomposites were lower compared to pure PMMA. Also, the thermal stability of nanocomposites in nitrogen and air was different from that of pure PMMA.     

Dynamics of Poly(methyl methacrylate) in Ionic Liquids with Different Concentration and Cationic Structures

The dynamic behavior of entangled poly(methyl methacrylate)(PMMA) chains in both the traditional monocationic ionic liquid(MIL)and synthetic dicationic ionic liquid(DIL) with the same anion bis[(trifluoromethyl)sulfonyl]imide([TFSI]-) has been examined over the wide composition range using differential scanning calorimetry and rheological measurements.PMMA/DIL and PMMA/MIL systems exhibit two glass transitions in the midrange of composition due to self-concentration effects.PMMA in DIL shows slo...