Stereocomplex formation in polybutadiene-syndiotactic poly(methyl methacrylate) block copolymers blended with isotactic poly(methyl methacrylate)

Summary The process of stereocomplexation in blends of isotactic poly(methyl methacrylate)s and polybutadiene-syndiotactic poly(methyl methacrylate) diblock copolymers was studied by differential scanning calorimetry as a function of molar mass of the constituents, annealing time and temperature. The amount of complex formed is dependent on these three parameters, while the temperature of decomposition of the complex is only dependent on the annealing temperature. Complex formation can be observed in blends containing a copolymer with a very low molar mass syndiotactic poly(methyl methacrylate) block (Mn=700). In contrast to homopolymer blends, for which two endotherms of decomposition were generally reported, only one endotherm is observed for copolymer-homopolymer blends. This behavior is attributed to the elastomer block.     

Effect of copolymer composition on the miscibility of blends of styrene-acrylonitrile copolymers with poly (methyl methacrylate)

The phase behaviour for blends of various polymethacrylates with styrene-acrylonitrile (SAN) copolymers has been examined as a function of the acrylonitrile content of the copolymer. Poly(methyl methacrylate), poly(ethyl methacrylate) and poly(n-propyl methacrylate) were found to be miscible with SANs over a limited window of acrylonitrile contents while no SANs appear to be miscible with poly(isopropyl methacrylate) or poly(n-butyl methacrylate). These conclusions were reached on the basis of lower critical solution temperature (LCST) and glass transition temperature behaviour. All miscible blends exhibited phase separation on heating, LCST behaviour, at temperatures which varied greatly with copolymer composition. An optimum acrylonitrile (AN) level ranging from about 10 to 14% by weight resulted in the highest temperatures for phase separation which has important implications for selection of SANs to produce homogeneous mixtures by melt processing. The basis for miscibility in these systems is evidently repulsion between styrene and acrylonitrile units in the copolymer as explained by recent models. The excess volumes for all blends are zero within experimental accuracy which suggests that the interactions for miscibility are relatively weak even for the optimum AN level. This interaction becomes smaller the larger or more bulky is the alkyl side group of the polymethacrylate.     

Phase behaviour and phase separation in polymer blends of poly(methyl methacrylate) with poly(vinyl acetate)

Summary Phase behaviour and phase separation in a binary polymer blends of poly(methyl methacryate) (PMMA) with poly(vinyl acetate) (PVAc) was invistigated by cloud method and light scattering. A lower critical solution temperature (LCST) type phase diagram was found. The mixture system of PMMA/PVAc is miscible. Kinetic study on demixing at the two-phase region above the LCST was carried out by light scattering.     

聚甲基丙烯酸甲酯/环氧树脂互穿网络复合物的性能研究

使用环氧树脂（EP-618）对作为人工义齿材料的聚甲基丙烯酸甲酯进行了共混改性,通过使用胺类固化剂（XCT-802）、甲基六氢邻苯二甲酸酐（MeHHPA）及2-乙基-4-甲基咪唑（2E4MZ）3种不同类型的固化体系,经过物理共混及化学反应的方法制备出具有互穿网络结构的聚甲基丙烯酸甲酯／环氧树脂二元复合物,并讨论了不同环氧树脂用量对该复合物力学性能的影响。     

Phase separation during crosslinking of epoxy resin/poly(ethylene oxide) blends

Summary Poly(ethylene oxide) (PEO) was found to be miscible with uncured epoxy resin of DGEBA type (ER) as shown by the existence of a single glass transition temperature (Tg) in each blend. However, PEO with ¯Mn = 20,000 was judged to be immiscible with the highly aminecross linked ER. It was observed that the phase separation in the ER/PEO blends occurred as the crosslinking progressed. This is considered to be due to the dramatical change in the chemical and physical nature of ER during the crosslinking.     

Conductive blends of polyaniline with plasticized poly(methyl methacrylate)

Polyaniline (PANI) protonated with camphorsulfonic acid (CSA) and three different poly(alkylene phosphates) (PAPs) (where alkylene = pentylene, hexylene, or nonylene) was used in the fabrication of conductive polyaniline–poly(methyl methacrylate) (PMMA) blends. The lowest percolation threshold (f_p = 0.041 wt %) was obtained for the PANI(CSA)_0.5–PMMA blend plasticized with 35 wt % of dibutyl phtalate (DBPh). This blend is also very resistant against the deprotonation of its conductive phase in basic solutions of pH = 9. In the case of blends prepared with the use of PAPs as PANI dopants, the percolation threshold strongly depends on the length of the hydrophobic spacer (alkylene group) in the dopant. The percolation threshold decreases in the order PPP > PHP > PNP, whereas the resistance against deprotonation in basic solutions decreases in the following inverse order: PNP > PHP > PPP. This last observation can be rationalized by increasing contribution of hydrophobic segments in the polymeric dopant, when going from PPP to PNP, which renders polyaniline more resistance toward the penetration by aqueous basic solutions. © 1999 John Wiley & Sons, Inc. J Appl Polym Sci 74: 471–479, 1999     

Phase separation of poly (methyl methacrylate) / poly (styrene-co-acrylonitrile) blends in the presence of silica nanoparticles

The effects of silica nanoparticles on the phase separation of poly (methyl methacrylate)/poly (styrene-co-acrylonitrile) (PMMA/SAN) blends are studied by the rheological method. The binodal temperatures of near-critical compositions were obtained by the gel-like behavior during spinodal decomposition, which is a character of polymer blends with co-continuous morphology. The shifted Cole–Cole plot method was introduced to determine the binodal temperatures of off-critical compositions based on the appearance of shoulder-like transition in the terminal regime of blends with droplet morphology. Such method is found also applicable in nanoparticle filled polymer blends. Moreover, a new method to determine the spinodal temperature from Fredrickson-Larson mean field theory was suggested, where the concentration fluctuation's contribution to the storage modulus is used instead of the whole dynamic moduli. This method was also successfully extended to nanoparticle filled polymer blend. The influences of the concentration and the average diameter of silica particles on the phase separation temperature were studied. It was found that the small amount of the silica nanoparticles in PMMA/SAN blends will significantly change the phase diagram, which is related to the selective location of silica in PMMA. The comparisons with thermodynamic theory of particle-filled polymer blends are also discussed.     

Reaction-induced microphase separation in polybenzoxazine thermosets containing poly(N-vinyl pyrrolidone)-block-polystyrene diblock copolymer

Poly(N-vinyl pyrrolidone)-block-polystyrene diblock copolymer (PVPy-b-PS) was synthesized via sequential reversible radical-fragmentation transfer polymerization with S-1-phenylethyl O-ethylxanthate as a chain transfer agent. The block copolymer was incorporated into polybenzoxazine to access the nanostructures in the thermosets. The nanostructures in the thermosets were investigated by means of transmission electron microscopy (TEM) and small-angle X-ray scattering (SAXS). It was found that disordered and/or ordered PS nanophases were formed in the PBa thermosets. It is judged that the formation of nanophases followed the mechanism of reaction-induced microphase separation in terms of the miscibility of the subchains of the diblock copolymer (viz. PVPy and PS) with polybenzoxazine after and before curing reaction.     

Phase separation and mechanical properties of poly(methyl methacrylate)/polycarbonate blends

Dynamic mechanical properties, tensile properties, and scanning electron microscopy of blends of poly(methyl methacrylate) and polycarbonate were investigated after phase separation above their cloud point temperature by annealing in a hot press. The dynamic mechanical properties show that phase separation proceeds more distinctly for the blends annealed at higher temperature and for longer time. The scanning electron micrographs show that the morphology of phase separated blends varies with the conditions of heat treatment. The tensile properties of phase separated blends deteriorate on account of the coarsening of the brittle dispersed phase over the optimum size and the occurrence of voiding during the heat treatment.     

Study of polymer blends of poly(acetylene) with poly(methyl methacrylate) and methyl methacrylate-butadiene-styrene copolymer

Summary Electroactive polymer blends of polyacetylene (PA) with poly (methyl methacrylate) (PMMA) or methyl methacrylate-butadien-styrene (MBS) copolymer were prepared in situ as free-standing films or powders by polymerization of acetylene in the presence of PMMA or MBS-copolymer, using Luttinger's catalyst. Blends of different composition were studied by infrared spectroscopy and electrical conductivity measurements. Environmental stability of pristine and doped PA was improved to some extent in the presence of PMMA.     

Viscoelastic behaviour of epoxy resins modified with poly(methyl methacrylate)

The viscoelastic behaviour of a stoichiometric diglycidyl ether of bisphenol-A, (DGEBA), 4,4′-diaminodiphenylmethanes (DDM)s epoxy matrix modified with several amounts of poly(methyl methacrylate) (PMMA) has been studied by dynamic-mechanical analysis. Mixtures pre-cured at 80°C ranged from transparency to opacity as thermoplastic content changed from 5 to 15wt%. These changes have been attributed to variations in the ratio between polymerization rate and phase separation rate when PMMA content increased in the mixtures. When PMMA segregated from the epoxy matrix during curing, it had no influence on the crosslinking density of the epoxy phase. The clear decrease of temperature and activation energy of the β relaxation with respect to those values for the neat matrix, observed for the 5wt% PMMA-containing mixture but not for the 15wt% PMMA-containing one, are proposed to be a consequence of physical interactions between the PMMA chains and some epoxy oligomers. The dissimilar variation of the height of the ω relaxation with frequency when compared to that for the other relaxations studied, outlines the significance of physical factors influencing this relaxation. © 1998 Society of Chemical Industry     

The miscibility and phase separation in binary blends of poly(ethyl methacrylate) with styrene/acrylonitrile copolymers

Summary The miscibility and lower critical solution behaviour of pol(ethyl methacrylate) with poly(styrene-stat-acrylonitrile) have been studied. Poly(ethyl methacrylate) is miscible with styrene/acrylonitrile copolymers having acrylonitrile concents between 9 and 34 wt %. By increasing the size of the pendant group from methyl to ethyl, the repulsive interaction between the methacrylate and acrylonitrile increases, but that between the methacrylate and styrene decreases.     

High heat resistant blends of poly(methyl methacrylate) and styrenic copolymers via post reactor modification

This work focuses on the methodology to obtain high heat resistant grades of poly(methyl methacrylate) (PMMA) without affecting any of the enabling properties of PMMA through the post reactor modification approach. The post reactor modification approach has been employed to obtain high heat resistant grades of PMMA through blending of PMMA with the high heat copolymers namely, styrene maleic anhydride copolymers (SMA) which have a higher glass transition temperature (T_g) than that of PMMA. The optimum levels of maleic anhydride content (MA %) in the SMA and the preferred composition range of PMMA and SMA blends have been identified wherein the heat properties of PMMA improve substantially without affecting the key properties of PMMA such as optical clarity, mechanical, flow, scratch, and weatherability. There are various analytical tools that are being employed to characterize the resulting blends of PMMA and SMA to gain deeper understanding from the fundamental behavior of these blends for the key applications of interest. © 2018 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2018 , 135, 46220.     

Interactions in poly(vinylidene fluoride)/poly(methyl methacrylate-co-ethyl methacrylate) blends

Summary The interaction parameters B for blends of poly(vinylidene fluoride) (PVDF) with poly(methyl methacrylate) (PMMA), poly(ethyl methacrylate) (PEMA) and five methyl methacrylate/ ethyl methacrylate copolymers (PMEMA) were determined by measurements of melting point depression of PVDF. The B values are negative, indicating an attractive intermolecular interaction. The intramolecular interaction parameter between MMA and EMA segments in PMEMA was found to be +3.25 cal/cm³, indicating a repulsive interaction between different monomer segments in the copolymer.     

Separation of poly(styrene–methyl methacrylate) block copolymers by liquid adsorption chromatography

Block copolymers P(S-b-MMA) prepared by using polymeric peroxide as an initiator were separated into three peaks using silica gel as an adsorbent and a mixture of chloroform and ethanol as the mobile phase. The first peak included both polystyrene homopolymer and P(S-b-MMA), the second peak appeared to be P(S-b-MMA), and the third consisted of P(S-b-MMA) and poly(methyl methacrylate) homopolymer. These results suggest the presence of three different block copolymers in composition and/or in structure. By removing the two homopolymers, it was found that the P(S-b-MMA) sample prepared in this work consisted of two components of equal amount: One was a block copolymer having a smaller MMA content and smaller molecular weight averages and the other having a higher MMA content (similar to the monomer feed ratio) and higher molecular weight. Besides these two components, one minor copolymer, which might be different from these two components but rather similar to the first one in both composition and molecular weight, appeared between these two peaks in a liquid adsorption chromatogram. These three components had both composition and molecular weight distributions.     

Poly(ethylene oxide)/poly(methyl methacrylate) blends: Influence of tacticity of poly(methyl methacrylate) on blend structure and miscibility

The influence of different configurations of poly(methyl methacrylate) on the miscibility and superstructure of poly(ethylene oxide)/poly(methyl methacrylate) (PEO/PMMA) blends was examined using small-angle X-ray scattering and differential scanning calorimetry. The blends prepared by solution casting were isothermally crystallized at 48°C. The miscibility, the melting behaviour, the glass transition temperature and the structural parameters of the blends were strongly dependent on the tacticity and blend composition. The small-angle X-ray intensity profiles were analysed using a recently developed methodology. For the poly(ethylene oxide)/atactic poly(methyl methacrylate) (PEO/APMMA) and poly(ethylene oxide)/syndiotactic poly(methyl methacrylate) (PEO/SPMMA) blends, the long period and the amorphous and transition region thicknesses increased with increase of PMMA content, whereas for the poly(ethylene oxide)/isotactic poly(methyl methacrylate) (PEO/IPMMA) blends they are independent of composition. The structural properties of the blends were attributed to the presence of non-crystallizable material in the interlamellar or interfibrillar regions, depending on PMMA tacticity. From the glass transition and melting temperatures, it has been supposed that one homogeneous amorphous phase is present in the case of PEO/APMMA and PEO/SPMMA blends and that the PEO/IPMMA amorphous system is phase-separated. The free-volume contribution to the energy of mixing for the various tactic PMMAs is hypothesized to be responsible for the difference in mixing behaviour.     

Spherulitic crystallization in blends of poly(ethylene oxide) and poly(methyl methacrylate)

The crystallization kinetics of binary blends of poly(ethylene oxide) and poly(methyl methacrylate) were investigated. The isothermal spherulitic growth rates were measured by means of a polarized light microscope. The temperature and composition dependence on the growth rates have been analysed. The temperature range studied was from 44° to 58°C. The introduction of poly(methyl methacrylate) into poly(ethylene oxide) resulted in a reduction of the spherulitic growth rate as the proportion of poly(methyl methacrylate) was increased from zero to 40% by weight. Results have been analysed using the theoretical equations of Boon and Azcue for the growth rate of polymer-diluent mixtures. The experimental results are in good agreement with this equation. The temperature coefficient is negative as is the case in the crystallization of bulk homopolymers.     

Degradation kinetics of poly(ethylene terephthalate) and poly (methyl methacrylate) blends

Summary Poly(ethylene terephthalate) PET and poly(methyl methacrylate) PMMA blends were made by melt mixing in a batch reactor. Three different weight ratios of PET : PMMA (25:75, 50:50 and 75:25) were chosen to study the effect of blend composition on the degradation kinetics. A relationship between the fractional volatiles evolved per unit time and the fraction of polymer degraded is established. The kinetic parameters for degradation were found using modified Avrami’s non-isothermal equation. Parameters like degradation rate constant (k) and order of degradation (n), were evaluated for the virgin polymers and the blends.