Reactive Compatibilization of PA6/LDPE Blends with Glycidyl Methacrylate Functionalized Polyolefins

Summary: Blends of polyamide‐6 (PA6) and low density polyethylene (LDPE) were compatibilized by melt mixing with various polyolefins functionalized with glycidyl methacrylate (GMA), i.e., GMA grafted LDPE (LDPE‐g‐GMA), GMA grafted styrene‐ethylene/butylene‐styrene block copolymer (SEBS‐g‐GMA) and ethylene‐co‐glycidyl methacrylate copolymer (E‐GMA). Blends with PA6/LDPE composition ratios of 25/75 and 75/25 wt.‐%/wt.‐% were prepared in a Brabender internal mixer and their properties were evaluated by SEM, rheological measurements and DSC. Morphological investigation by SEM showed a neat improvement of phase dispersion and interfacial adhesion in all compatibilized blends when compared to PA6/LDPE binary blends. The variation of the dispersed phase size was analyzed as a function of blend composition, compatibilizer concentration and GMA content. The emulsification curves of compatibilized blends showed that the equilibrium size of dispersed particles at the saturation concentration of copolymer was lower when PA6 was the major component. The finest dispersion of the LDPE phase (<0.25 μm) was observed in the presence of SEBS‐g‐GMA copolymer. LDPE‐g‐GMA and E‐GMA displayed a similar compatibilizing efficiency. In all cases, the blends with a polyamide matrix presented a marked rise in torque and melt viscosity with increasing compatibilizer content. These effects were accounted for by a reaction between the epoxide groups of LDPE‐g‐GMA and the carboxyl/amine end‐groups of PA6, leading to the formation of an interchain graft copolymer. The phase transition processes of PA6 in the blends were influenced by the compatibilizer content and the interfacial interactions between the polymer components, suggesting a different role for the compatibilizer at the PA6/LDPE interface.

SEM micrograph of PA6/LDPE 25/75 blend compatibilized with 2.5 phr SEBS‐g‐GMA.     

Improved Electrical Performance of Poly(3‐hexylthiophene) Induced by Stable Doping with Polymer Dopants

A series of brominated polystyrenes (BPSs) are readily synthesized and blended as polymer dopants with the p‐type semiconducting polymer, poly(3‐hexylthiophene) (P3HT), to improve theirelectrical performance. The obtained P3HT/BPS blend films exhibit increased carrier concentration resulting from doping of P3HT by BPS, which leads to excellent electrical performance, including enhanced hole mobility and conductivity, and the conductivity or mobility increases with the bromination degree of BPS. Compared with conventional small molecular dopants, the polymer dopant, BPS, shows not only excellent doping stability, but also good solution processibility, which makes it a promising materials for fabrication of low cost, flexible, transparent, and high performance solution processable organic electronic devices.

     

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.

     

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.

     

Thermoelectric Performance of Mechanically Mixed BixSb2-xTe3—ABS Composites

In the current study, polymer-based composites, consisting of Acrylonitrile Butadiene Styrene (ABS) and Bismuth Antimony Telluride (Bi_xSb_2−xTe₃), were produced using mechanical mixing and hot pressing. These composites were investigated regarding their electrical resistivity and Seebeck coefficient, with respect to Bi doping and Bi_xSb_2-xTe₃ loading into the composite. Experimental results showed that their thermoelectric performance is comparable—or even superior, in some cases—to reported thermoelectric polymer composites that have been produced using other complex techniques. Consequently, mechanically mixed polymer-based thermoelectric materials could be an efficient method for low-cost and large-scale production of polymer composites for potential thermoelectric applications.     

How to Improve Physico-Chemical Properties of Silk Fibroin Materials for Biomedical Applications?—Blending and Cross-Linking of Silk Fibroin—A Review

This review supplies a report on fresh advances in the field of silk fibroin (SF) biopolymer and its blends with biopolymers as new biomaterials. The review also includes a subsection about silk fibroin mixtures with synthetic polymers. Silk fibroin is commonly used to receive biomaterials. However, the materials based on pure polymer present low mechanical parameters, and high enzymatic degradation rate. These properties can be problematic for tissue engineering applications. An increased interest in two- and three-component mixtures and chemically cross-linked materials has been observed due to their improved physico-chemical properties. These materials can be attractive and desirable for both academic, and, industrial attention because they expose improvements in properties required in the biomedical field. The structure, forms, methods of preparation, and some physico-chemical properties of silk fibroin are discussed in this review. Detailed examples are also given from scientific reports and practical experiments. The most common biopolymers: collagen (Coll), chitosan (CTS), alginate (AL), and hyaluronic acid (HA) are discussed as components of silk fibroin-based mixtures. Examples of binary and ternary mixtures, composites with the addition of magnetic particles, hydroxyapatite or titanium dioxide are also included and given. Additionally, the advantages and disadvantages of chemical, physical, and enzymatic cross-linking were demonstrated.     

安妥碘(Entodon)配伍剂超声药浴治疗脉络视网膜炎的临床应用

目的 探讨药物通过超声雾化后洗浴眼部组织治疗眼球后节某些疾病的方法和疗效.方法 在门诊接受超声药浴治疗386例(492只眼)中有20例临床诊断为脉络膜视网膜炎28只眼,通过安妥碘配伍剂超声药浴治疗,定期测量视力,记录症状改变,观察眼底情形,询问不适情况.结果 经过安妥碘配伍剂超声药浴治疗后,28只眼通过标准对数视力表测量,视力提高0.2及0.2以上有26只眼,两只眼治疗前视力均为30cm数指,治疗后一只眼达0.08,另一只眼达0.15.治疗后眼底检查渗出水肿均有改善.所有超声药浴治疗患者,无重大不良并发症.结论 :安妥碘配伍剂超声药浴治疗脉络膜视网膜炎,有控制病情、恢复视网膜功能的良好作用.治疗简捷、有效、安全.     

The Effect of Alcohol Compound on the Solidification of Magnesium Oxysulfate Cement-Boron Mud Blends

At present, the utilization of boron resources in China is increasing, and the problem of boron tailing pollution is becoming increasingly serious. To fundamentally solve the problem of boron tailing, many scholars at home and abroad have mainly studied the curing effect in terms of compressive strength, and little research has been carried out into the solidification effect and hydration products. This study explored the effects of adding different alcohol-based modifiers on the hydration products of magnesium oxysulfate cement-boron mud mixture, the microstructure, physical properties and curing effects of the samples. The results show that magnesium oxysulfate cement is beneficial to the solidification of boron in boron mud due to its low-alkali. Adding an alcohol-based modifier can increase the compressive strength of magnesium oxysulfate cement-boron mud blends. After adding acrylic acid and D-Mannitol, the 28-day compressive strength of the sample increased by 44.7 MPa. The blending of alcohol-based modifiers has a very good effect on the curing of boron in the whole system.     

Unexpected Rheology of Polydimethylsiloxane Liquid Blends

The rheological behaviour of polydimethylsiloxane (PDMS) liquid blends has been investigated both in rotational and oscillating mode. Liquid silicone rubbers based on PDMS at low, medium, and high viscosity have been used for low/high or medium/high liquid blends. The flow, viscosity, creep, and stress‐relaxation curves, strain‐spectra of temperature‐ or frequency‐sweep have been determined and the behaviour at slow shear rate investigated in detail. The low/high homologous blend shows an unexpected behaviour: the zero‐shear viscosity η₀ is higher, the compliance J ₀ lower and viscoelastic moduli G ₀, G(t), G′(ω) and G″(ω) higher, with respect to the components and medium/high blend. Moreover, the blend viscosity η(T), G′(T), and G″(T) exhibits an anomalous decreasing trend. The Entanglement Swelling Tube (EST) model is proposed. The nanosized chains swelled the entanglement of the long ones by means of dipolar interactions ? Si ^{δ +}–O ^{δ ?} in the sites between the blobs of the tube chains, where the free‐volume is highest. The linked entanglements are stabilized and the lifetime lengthened; the entanglement density increases at long deformation times. As the temperature rises, the anomalous behaviour is reduced due to the Entanglement Deswelling‐Solvation mechanism of short chains up to the transition to ordinary behaviour for T = 65 °C.     

A novel approach for analyzing glass-transition temperature vs. composition patterns: Application to pharmaceutical compound + polymer systems

In medicine, polymer-based materials are commonly used as excipients of poorly water-soluble drugs. The success of the encapsulation, as well as the physicochemical stability of the products, is often reflected on their glass transition temperature (T_g) vs. composition ($w$) dependencies. The shape of the $T_{\text{g}}(w)$ patterns is critically influenced by polymer's molecular mass, drug molecule's shape and molecular volume, the type and degree of shielding of hydrogen-bonding capable functional groups, as well as aspects of the preparation process. By altering mixture's T_g the amorphous solid form of the active ingredient may be retained at ambient or body temperatures, with concomitant improvements in handling, solubility, dissolution rate and oral bioavailability. Given the importance of the problem, the glass transitions observed in pharmaceutical mixtures have been extensively analyzed, aiming to appraise the state of mixing and intermolecular interactions. Here, accumulated experimental information on related systems is re-evaluated and comparably discussed under the light of a more effective and system-inclusive $T_{\text{g}}(w)$ equation. The present analysis indicates that free volume modifications and conformational changes of the macromolecular chains dominate, over enthalpic effects of mixing, in determining thermal characteristics and crystallization inhibition/retardation. Moreover, hydrogen-bonding and ion-dipole heterocontacts – although favorable of a higher degree of mixing – appear less significant compared to the steric hindrances and the antiplasticization proffered by the higher viscosity component.