PMMA Phase Research Articles

Bulk phase behavior of tetra-n-butylammonium bromide hydrates formed with carbon dioxide or methane gas

We report the bulk phase behavior of ionic clathrate hydrates of tetra-n-butylammonium bromide (TBAB) formed with a common guest substance: CO2 or CH4. We formed the bulk samples by a classical mixing reactor for gas hydrates, and measured them by the powder X-ray diffraction (PXRD). PXRD patterns of the TBAB+(CO2 or CH4) hydrates formed with 0.32 of TBAB mass fraction in the aqueous phase were obtained. They are consistent with the orthorhombic hydrate (Shimada et al., Acta Crystallogr. 2005; Muromachi et al., Chem. Commun. 2014), but not identical with the other stable phase, i.e., the tetragonal TBAB hydrate (Rodionova et al., J. Phys. Chem. B 2013). When the aqueous solutions are under the substantial pressure of CO2 or CH4 gas, TBAB is likely to form the orthorhombic Pmma and/or Imma phases. A question for the bulk orthorhombic TBAB hydrate phase about the scarce gas incorporation is newly proposed.

Ionogels Based on Poly(methyl methacrylate) and Metal-Containing Ionic Liquids: Correlation between Structure and Mechanical and Electrical Properties.

Ionogels (IGs) based on poly(methyl methacrylate) (PMMA) and the metal-containing ionic liquids (ILs) bis-1-butyl-3-methlimidazolium tetrachloridocuprate(II), tetrachloride cobaltate(II), and tetrachlorido manganate(II) have been synthesized and their mechanical and electrical properties have been correlated with their microstructure. Unlike many previous examples, the current IGs show a decreasing stability in stress-strain experiments on increasing IL fractions. The conductivities of the current IGs are lower than those observed in similar examples in the literature. Both effects are caused by a two-phase structure with micrometer-sized IL-rich domains homogeneously dispersed an IL-deficient continuous PMMA phase. This study demonstrates that the IL-polymer miscibility and the morphology of the IGs are key parameters to control the (macroscopic) properties of IGs.

Enhancing the electrical conductivity of carbon black-filled immiscible polymer blends by tuning the morphology

Blends of carbon black (CB)-filled polystyrene (PS) and poly(methyl methacrylate) (PMMA) with different PS/PMMA ratios have been prepared by melt blending in order to obtain conductive polymer composites with a low electrical percolation threshold according to the concept of double percolation. The dependence of the electrical conductivity on the morphology of the composite was examined before and after annealing in the molten state. The electrical conductivity of the composites was highest when the PS and PMMA phases formed a co-continuous structure and CB particles were selectively located and percolated in the PS phase. PS/PMMA (30/70) blends exhibited the lowest electrical percolation threshold of 1.26vol% CB. A simple model is suggested to explain this effect. After annealing, the CB clearly affected the stabilization of the co-continuous structure. Moreover, the electrical conductivity increased after annealing and the percolation threshold decreased to below 1vol% CB regardless of PS content. The largest increase in electrical conductivity after annealing was found with PS/PMMA (70/30) blends filled with 1vol% CB. With increasing PMMA content, this effect became less pronounced. The different behaviors in the composites can be explained by dynamic percolation and decrease in continuity of the CB-filled PS phase induced by structure coarsening.

Graft copolymerization of methyl methacrylate from brominated poly(isobutylene‐co‐isoprene) via atom transfer radical polymerization

ABSTRACTCommercial brominated poly(isobutylene‐co‐isoprene) (BIIR) rubber has been directly used for the initiation of atom transfer radical polymerization (ATRP) by utilizing the allylic bromine atoms on the macromolecular chains of BIIR. The graft copolymerization of methyl methacrylate (MMA) from the backbone of BIIR which was used as a macroinitiator was carried out in xylene at 85 °C with CuBr/N,N,N′,N″,N″‐pentamethyldiethylenetriamine as a catalytic complex. The polymerization conditions were optimized by adjusting the catalyst and monomer concentration to reach a higher monomer conversion and meanwhile suppress macroscopic gelation during the polymerization process. This copolymerization followed a first‐order kinetic behavior with respect to the monomer concentration, and the number‐average molecular weight of the grafted poly(methyl methacrylate) (PMMA) increased with reaction time. The resultant BIIR‐graft‐PMMA copolymers showed phase separation morphology as characterized by atomic force microscopy, and the presence of PMMA phase increased the polarity of the BIIR copolymers. This study demonstrated the feasibility of using commercial BIIR polymer directly as a macromolecular initiator for ATRP reactions, which opens more possibilities for BIIR modifications for wider applications. © 2016 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2016, 133, 43408.

Synthesis and properties of PMMA‐ZrO2 organic–inorganic hybrid films

ABSTRACTIn this work we report the synthesis process and properties of PMMA‐ZrO2 organic–inorganic hybrid films. The hybrid films were deposited by a modified sol‐gel process using zirconium propoxide (ZP) as the inorganic (zirconia) source, methyl methacrylate (MMA) as the organic source, and 3‐trimetoxy‐silyl‐propyl‐methacrylate (TMSPM) as the coupling agent between organic and inorganic phases. The films were deposited by dip coating on glass slide substrates from a hybrid precursor solution containing the three precursors with molar ratio 1 : 0.25 : 0.25 for ZP, TMSPM, and MMA, respectively. After deposition, the hybrid thin films were heat‐treated at 100°C for 24 h. The macroscopic characteristics of the hybrid films such as high homogeneity and high optical transparence evidenced the formation of a cross‐linked, interpenetrated organic–inorganic network. The deposited PMMA‐ZrO2 hybrid films were homogeneous, highly transparent and very well adhered to substrates. Fourier Transform Infra‐Red measurements of the hybrid films display absorption bands of chemical groups associated with both PMMA and ZrO2 phases. The amounts of organic and inorganic phases in the hybrid films were determined from thermogravimetric measurements. The surface morphology and homogeneity of the hybrid films at microscopic level were analyzed by scanning electron microscopy and atomic force microscopy images. From the analysis of optical transmission and reflection spectra, the optical constants (refraction index and extinction coefficient) of the hybrid films were determined, employing a physical model to simulate the hybrid optical layers. The refraction index of the hybrid films at 532 nm was 1.56. © 2015 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2015, 132, 42738.

Preparation of waterborne self-cleaning nanocomposite coatings based on TiO2/PMMA latex

Abstract Titania/poly(methyl methacrylate) core/shell (TiO 2 /PMMA) latex was synthesized by miniemulsion polymerization and further mixed with modified colloidal silica to create waterborne nanocomposite coatings (M-SiO 2 /TiO 2 /PMMA). The coatings were undergone accelerated weathering tests and their surface wettability, transparency, and morphology were monitored as a function of weathering time. Superhydrophilic surfaces were attained after 27–34 h aging, being attributed to the unique distribution of TiO 2 nanoparticles in PMMA phase. In contrast to the coating based on the mixture of M-SiO 2 , TiO 2 nanoparticles, and PMMA latex, this time is quite short and absolutely benefit for their outdoor application. Due to the degradation of organic matrix, transparency reduction and film thickness loss of coatings took place in weathering tests. Nevertheless, these undesired evolutions can be alleviated by decreasing film thickness or using adequate quantity of TiO 2 /PMMA latex. Photodegradation experiments of methyl blue indicate that the formed superhydrophilic coatings are excellent in self-cleaning performance.

Morphology control of PS-b-PB-b-PMMA/PMMA blends by silica nanoparticles

The effect of the silica nanoparticles on the morphology of a blend consisting of poly(methyl methacrylate) (PMMA) and the poly(styrene)-b-poly(butadiene)-b-poly(methyl methacrylate) (SBM) triblock copolymer was studied. Upon blending PMMA with SBM, macrophase separation between the block copolymer and homopolymer occurred, in which the higher molar mass chains of homopolymer separate into homopolymer-rich domains due to the ‘dry-brush’ regime, whereas the lower molar mass chains of homopolymer tend to be selectively solubilized in the block copolymer-rich domains due to the ‘wet-brush’ regime. Upon adding the hydrophilic silica nanoparticles to the PMMA/SBM blend, a significant suppression effect on the extent of macrophase separation between the homopolymer and block copolymer can be observed. It was shown that the silica particles are preferentially localized in the PMMA phase due to the strong hydrogen bonding interaction between the hydroxyl groups on the surface of silica nanoparticles with the carbonyl groups of the PMMA. The suppression effect of the silica particles may be related to the selective adsorption of the high molar mass PMMA on the surface of the silica particles, which may force the system into the ‘wet-brush’ regime, but this was only observed for the systems with a low silica content. For the systems with a high silica content, both the homopolymer PMMA and the PMMA block of the SBM block copolymer interact with the silica surface, which becomes the connecting part between both polymers, thereby suppressing the extent of macrophase separation.

Preparation of hemispherical particles by cleavage of micrometer-sized, spherical polystyrene/poly(methyl methacrylate) composite particles with Janus structures: effect of polystyrene-b-poly(methyl methacrylate)

We recently reported that two micrometer-sized, hemispherical polymer particles were prepared as a result of the cleavage of spherical Janus polystyrene (PS)/poly(methyl methacrylate) (PMMA) composite particles after treatment with acetone. The original composite particles were prepared by slow evaporation of toluene from homogeneous PS/PMMA/toluene droplets dispersed in an aqueous solution of sodium dodecyl sulfate. This article aims to validate a proposed cleavage mechanism which is based on the induction of internal stress at the interface because of a great difference in the swelling ratio between the PS and PMMA phases. The effect of PS-b-PMMA, which should exist at the interface between both phases and decrease the internal stress, on the cleavage phenomenon was examined. PS/PS-b-PMMA/PMMA composite particles were prepared in the same way as the previous study. At 0.31 wt% or greater of PS-b-PMMA (number-average molecular weight: 10.6 × 104–b-9.9 × 104), the composite particles did not have a Janus structure but an ex-centered core-shell structure, resulting in no cleavage. At 0.18 wt% or less, they had a Janus structure, and the cleavage phenomenon was observed. The required time to cleave increased with increasing PS-b-PMMA content to below 0.18 wt%. Specifically, the existence of PS-b-PMMA delayed the cleavage of the composite particles into PS and PMMA hemispherical particles. This result supports the proposed cleavage mechanism and provides a tool to easily address the cleavage process for the production of hemispherical particles. Relationships between the interfacial area between PS and PMMA in a PS/PMMA (1/1, w/w) composite particles including various amounts (white circles 0; filled circles 0.05; white triangles 0.11; filled triangles 0.18 (wt % relative to the total amount of PS and PMMA)) of PS-b-PMMA (B11:Mn 10.6 × 104–b-9.9 × 104) and the required time to cleave into two parts (cleavage time, Tc) by addition of the acetone/water (9:1, v/v) solution to the dried particles

The Morphological properties of SnCl2·2H2O-modified PC/PMMA blends

SnCl2·2H2O-modified PC/PMMA (80/20 w/w) blends were prepared by melt blending using a torque rheometer. The effect of SnCl2·2H2O content and blending conditions on the structures, phase morphologies and thermal properties of the blends were investigated by FTIR, SEM, TGA and DSC. The FTIR spectra of the 0.015 % (wt) SnCl2·2H2O-modified PC/PMMA blends showed the characteristic peaks of both PC and PMMA due to the formation of PC-g-PMMA copolymers. From the SEM images, it was demonstrated that the domain size of the dispersed PMMA phase decreased clearly with the increases in SnCl2·2H2O content and the mixing time, but it increased with the incremental increases in the rotor rate before reaching 80 rpm. In addition, a similar co-continuous structure was observed in the two blend systems. The first blend was prepared at a temperature of 270 °C and a rotor rate of 40 rpm for 10 min, and the other blend was prepared at a temperature of 230 °C and a rotor rate of 70 rpm for 10 min. The TGA results showed that there was only one single-step thermal degradation in PC/PMMA blends which contained 0.100 % (wt) SnCl2·2H2O, suggesting the formation of a homogeneous blend of the two phases. The DSC curves demonstrated that the 0.015 % (wt) SnCl2·2H2O modified the PC/PMMA blend systems which were prepared at 230, 240 or 250 °C and displayed only one single glass transition temperature (T g). But, it showed two distinct T gs when the mixing temperature was set at 260 and 270 °C.

Structural analysis of polyolefin-poly(methyl methacrylate) blends

Polyethylenes (PEs) of different type and crystallinity (LDPE, HDPE and UHMWPE) were used to prepare blends of 80/20 ratio with poly(methyl methacrylate) (PMMA) and to evaluate their mechanical and structural properties. Methyl methacrylate monomer was mixed with the polyethylenes and the mixture was irradiated to in situ form the PMMA polymer, the blend and by expectation some copolymer. By evaluating the glass transition temperatures, insight can be gained in the structural changes within the PE and PMMA polymers. DSC and DMA tests yielded results where the characteristic transition temperature of the matrix polyethylene has shifted. After carrying out the DMA test, the samples were retested via DSC to evaluate the effect of the mechanical stresses. TSD method was used here to analyze the molecular movements in PE-PMMA blends. The results of the measurements show the appearance of PMMA phase in the polyethylene matrix, which inhibits the relaxation of crosslinked polyethylene. It is an unexpected behavior, because according to the calculations, PMMA and the PE should form an immiscible blend. These results indicate that during cyclic loading, the structure of the composition changed significantly. Its importance is that similar cyclic deformations/loads affect the hip joint implants also. The wear resistance of the prepared PE/PMMA 80/20 w/w % samples was measured using tribological methods, which show some improvement in all cases.

Preparation and Characterization of Injectable Brushite Filled-Poly (Methyl Methacrylate) Bone Cement.

Powder-liquid poly (methyl methacrylate) (PMMA) bone cements are widely utilized for augmentation of bone fractures and fixation of orthopedic implants. These cements typically have an abundance of beneficial qualities, however their lack of bioactivity allows for continued development. To enhance osseointegration and bioactivity, calcium phosphate cements prepared with hydroxyapatite, brushite or tricalcium phosphates have been introduced with rather unsuccessful results due to increased cement viscosity, poor handling and reduced mechanical performance. This has limited the use of such cements in applications requiring delivery through small cannulas and in load bearing. The goal of this study is to design an alternative cement system that can better accommodate calcium-phosphate additives while preserving cement rheological properties and performance. In the present work, a number of brushite-filled two-solution bone cements were prepared and characterized by studying their complex viscosity-versus-test frequency, extrusion stress, clumping tendency during injection through a syringe, extent of fill of a machined void in cortical bone analog specimens, and compressive strength. The addition of brushite into the two-solution cement formulations investigated did not affect the pseudoplastic behavior and handling properties of the materials as demonstrated by rheological experiments. Extrusion stress was observed to vary with brushite concentration with values lower or in the range of control PMMA-based cements. The materials were observed to completely fill pre-formed voids in bone analog specimens. Cement compressive strength was observed to decrease with increasing concentration of fillers; however, the materials exhibited high enough strength for consideration in load bearing applications. The results indicated that partially substituting the PMMA phase of the two-solution cement with brushite at a 40% by mass concentration provided the best combination of the properties investigated. This alternative material may find applications in systems requiring highly injectable and viscous cements such as in the treatment of spinal fractures and bone defects.

Gelation of Solvate Ionic Liquid by Self-Assembly of Block Copolymer and Characterization as Polymer Electrolyte

We report a new class of polymer electrolytes that exhibit high Li+-ionic conductivity and thermal stability up to 200 °C. The polymer electrolyte consists of a solvate ionic liquid ([Li(G4)][TFSA]), comprising an equimolar mixture of lithium bis(trifluoromethanesulfonyl)amide (Li[TFSA]) and tetraglyme (G4), and a well-defined ABA-triblock copolymer, polystyrene-b-poly(methyl methacrylate)-b-polystyrene (PSt-b-PMMA-b-PSt, SMS). The electrolyte is formed by the self-assembly of SMS, where the solvatophobic PSt segments serves as physical cross-linking points, and the solvatophilic PMMA segment with preferentially dissolved [Li(G4)][TFSA] forms ion-conduction paths. In the electrolyte, the preservation of the complex cation [Li(G4)]+ in the PMMA phase was demonstrated by pulsed-field gradient spin–echo (PGSE) NMR, Raman spectra, and thermogravimetric analysis. Because of the preservation of [Li(G4)]+, which hinders the direct interaction of Li+ with the polymer segment and the coupling of the ionic transport from the segmental motion, the room temperature ionic conductivity of the electrolyte reached an appreciable level (10–4–10–3 S cm–1).

Temperature influence and CO2 transport in foaming processes of poly(methyl methacrylate)–block copolymer nanocellular and microcellular foams

Fabricated by high-pressure or supercritical CO2 gas dissolution foaming process, nanocellular and microcellular polymer foams based on poly(methyl methacrylate) (PMMA homopolymer) present a controlled nucleation mechanism by the addition of a methylmethacrylate–butylacrylate–methylmethacrylate block copolymer (MAM), leading to defined nanocellular morphologies templated by the nanostructuration of PMMA/MAM precursor blends. Influence of the CO2 saturation temperature on the foaming mechanism and on the foam structure has been studied in 90/10 PMMA/MAM blends and also in the neat (amorphous) PMMA or (nanostructured) MAM polymers, in order to understand the role of the MAM nanostructuration in the cell growth and coalescence phenomena. CO2 uptake and desorption measurements on series of block copolymer/homopolymer blend samples show a competitive behavior of the soft, rubbery, and CO2-philic block of PBA (poly(butyl acrylate)) domains: fast desorption kinetics but higher initial saturation. This competition nevertheless is strongly influenced by the type of dispersion of PBA (e.g. micellar or lamellar) and a very consequent influence on foaming.CO2 sorption and desorption were characterized in order to provide a better understanding of the role of the block copolymer on the foaming stages. Poly(butyl acrylate) blocks are shown to have a faster CO2 diffusion rate than poly(methyl methacrylate) but are more CO2-philic. Thus gas saturation and cell nucleation (heterogeneous) are more affected by the PBA block while cell coalescence is more affected by the PMMA phases (in the copolymer blocks+in the matrix).

Structural and mechanical properties of GaAs under pressure up to 200 GPa

Ab initio calculations were performed for investigating the high pressure phases of GaAs up to 200GPa. By comparing the minimum free energies of structures, we found the thermodynamically stable phases of GaAs under pressure beyond GaAs-III (Imm2) with space groups Pmma and P4/nmm at the pressure range of 88–146GPa and 146–200GPa, respectively. For discussing the difference results of GaAs IV and V in previous studies, we found that Pmma and P4/nmm are the lower symmetric phases of P6/mmm and CsCl-like, respectively. For analyzing the Pmma→P4/nmm phase transition, we observed the approximated path and found that the barrier of transformation from Pmma to P4/nmm in direction [110] is 0.035eV. The graph of density of states shows no energy gap in stable phases at 130 and 160GPa, indicating that Pmma and P4/nmm are the metallic phases. The contour plots of the electron density difference show some valence electron sharing in Pmma which is higher than in P4/nmm. Moreover, the results of elastic parameters and modulus ratio suggested that the Pmma phase is a ductile material, while the P4/nmm phase is a brittle due to the increasing of shear modulus.

Sequential mixing as effective method in the reduction of percolation threshold of multiwall carbon nanotube in poly(methyl methacrylate)/high‐density poly(ethylene)/MWCNT nanocomposites

AbstractThis work demonstrates sequential heating protocol to be an effective method in the reduction of percolation threshold of multiwall carbon nanotube (MWCNT) in (70/30 w/w) poly(methyl methacrylate) (PMMA)/high‐density poly(ethylene) (HDPE)/MWCNT nanocomposites. Here, the percolation threshold (Pc) value was reduced to 0.08 wt % of MWCNT, which is the lowest among the ever reported values of Pc for the PMMA system. Moreover, a co‐continuous morphology of the minor HDPE phase was evident throughout the major PMMA phase in a highly asymmetric composition (70/30 w/w) of the blend constituents. The AC conductivity as well as the dielectric permittivity values were increased with increase in loading of MWCNT in the nanocomposites. The detailed analysis of electrical and morphological properties is discussed in depth in the article. © 2013 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2014, 131, 40235.

Concentration Fluctuations and Segmental Dynamics in Weakly Dynamic Asymmetric Blends in the Presence of Surface‐Functionalized Multiwall Carbon Nanotubes

Surface‐functionalized multiwall carbon nanotubes (MWCNTs) are incorporated in poly(methyl methacrylate)/styrene acrylonitrile (PMMA/SAN) blends and the pretransitional regime is monitored in situ by melt rheology and dielectric spectroscopy. As the blends exhibit weak dynamic asymmetry, the obvious transitions in the melt rheology due to thermal concentration fluctuations are weak. This is further supported by the weak temperature dependence of the correlation length (ξ ≈ 10–12 Å) in the vicinity of demixing. Hence, various rheological techniques in both the temperature and frequency domains are adopted to evaluate the demixing temperature. The spinodal decomposition temperature is manifested in an increase in the miscibility gap in the presence of MWCNTs. Furthermore, MWCNTs lead to a significant slowdown of the segmental dynamics in the blends. Thermally induced phase separation in the PMMA/SAN blends lead to selective localization of MWCNTs in the PMMA phase. This further manifests itself in a significant increase in the melt conductivity. image

The Control of Silica Nanoparticles on the Phase Separation of Poly(methyl methacrylate)/Poly(styrene‐co‐acrylonitrile) Blends

The influence of silica nanoparticles on the lower critical solution temperature (LCST) phase behavior and phase‐separation kinetics of a blend consisting of poly(methyl methacrylate) (PMMA) and poly(styrene‐co‐acrylonitrile) (SAN), is studied via a high‐throughput experimentation (HTE) approach, which combines a composition (φ) and a temperature (T) gradient. The evolution of the phase‐separation process is studied by optical microscopy (OM), small‐angle light scattering (SALS), and transmission electron microscopy (TEM). Depending on the specific interaction between the silica surface and the polymers, the distribution of silica particles during phase separation can be controlled to be either in one of the polymer phases or at the PMMA/SAN interface. The hydrophilic silica nanoparticles preferentially migrate to the PMMA phase, leading to a slow down of the coarsening rate, which may be related to a reduction of the mobility of PMMA due to an increase of the silica concentration. The hydrophobic silica nanoparticles are localized at the PMMA/SAN interface, and the inhibition of coalescence corresponds to the presence of a solid barrier (the nanoparticles) between the polymers, which prevents the coarsening process. image

Significant reinforcement of poly(propylene carbonate): Nanostructured polymer composites of poly(propylene carbonate)/poly(methyl methacrylate) via a supercritical carbon dioxide route

Biodegradable poly(propylene carbonate) (PPC) matrix composite with a significant improvement in yield strength was successfully prepared by incorporating a low content of poly(methyl methacrylate) (PMMA) via a supercritical carbon dioxide route. Atomic force microscopy measurement shows that the size of the dispersed PMMA phase in the PPC substrate is in the range from 50nm to 200nm, which is much smaller than the smallest ones that can be obtained by conventional melt blending method. Tensile tests demonstrate the excellent mechanical properties of the composites prepared in this study. By incorporating only 5wt% PMMA, the obtained composites show approximately 4 times higher yield strength than pure PPC and the elongation at break of the composites is well remained. By comparing with the reported works, this method shows the highest enhancement efficiency of PPC. The significant reinforcement of PPC is ascribed to the nano size phase-separated domains of rigid PMMA. These findings show an effective modification method of PPC for the potential alternative to the non-biodegradable polymers.

PLLA/PMMA blends: A shear-induced miscibility with tunable morphologies and properties?

Polymer blends and alloys represent an interesting approach to implement bio-based poly(l-lactic acid) (PLLA) into high-value applications. Here, a re-evaluation of the miscibility extent between both biobased PLLA and petro-based poly(methyl methacrylate) (PMMA) is proposed in order to tune morphologies and properties of resulting blends upon either a solvent-casting method or a twin-screw extrusion. The solvent-casting process proved only able to produce immiscible blends with matrix–droplet or co-continuous morphologies in function of the blend composition and the immiscibility–miscibility transition is not observed for temperature lower than 250 °C. When melt-processed via extrusion technique, only miscible PLLA/PMMA blends were recovered all over the composition range, as observed by a single glass transition and a single α-relaxation transition at intermediate temperature between pure PLLA and pure PMMA as determined by DSC and DMTA, respectively. Miscibility was also observed at low shear rate with a phase-reversibility, demonstrating the absence of any reactions between PMMA and PLLA phases and the existence of a shear-sensitive clarity point. Homogenous and transparent PLLA/PMMA blends were easily produced with tunable thermomechanical and barrier properties against the blend composition. Glass transition temperature, α-relaxation temperature, thermal resistance and gas permeability were accurately controlled by the PMMA content, while maintaining impact strength and storage modulus in the same range than PLLA itself.

Structures and morphologies of in situ polymerized blends of PMMA and ASA

AbstractBlends of poly(methyl methacrylate), PMMA, and the elastomer ASA, a graft copolymer based on poly(acrylonitrile‐co‐styrene) (SAN) and acrylic rubber, were prepared by in situ polymerization and characterized according to structural, mechanical, thermal, and morphological properties. The polymerization conditions, such the presence or absence of a chain transfer agent, stirring and an inert atmosphere, influence the morphological and structural properties of the blends. In spite of the evidences of the partial miscibility between PMMA and SAN phase of the ASA, the blends are heterogeneous and present a complex morphology. The morphology of some PMMA‐ASA blends is made up of an elastomeric dispersed phase in a glassy matrix, with a possible inclusion of the matrix in the elastomeric domains. The selective extraction of the blend components and infrared spectroscopy showed that crosslinking and/or grafting reactions occur on ASA chains during MMA polymerization. The syndiotacticity of PMMA obtained in the presence of ASA increases with the amount of ASA, due to possible interactions between the carbonyl groups of PMMA and the nitrile or phenyl groups of the SAN copolymer. The mechanical properties of the blends were influenced by the compositions of the blends and mainly by the conditions of polymerization. © 2013 Wiley Periodicals, Inc. J. Appl. Polym. Sci., 2013