Influence of imide functionalized organo‐modified Mg‐Al layered double hydroxide on the thermal and mechanical properties of new aliphatic‐aromatic poly (amide‐imide)

A new dicarboxylic acid modified Mg‐Al LDH (DLDH) containing imide groups was prepared and its effects on the thermal and mechanical properties of the new synthesized aliphatic‐aromatic poly (amide‐imide) (PAI) were investigated via preparation of PAI/nanocomposite films by solution casting method. The results of X‐ray diffraction (XRD), field emission‐scanning electron microscopy (FE‐SEM) and transmission electron microscopy (TEM) showed a uniform dispersion for LDH layers into the PAI matrix. For comparison, the effects of polyacrylic acid‐co‐poly‐2‐acrylamido‐ 2‐methylpropanesulfonic acid (PAMPS‐co‐PAA) modified Mg‐Al LDH (ALDH) on the PAI properties were also studied. The thermogravimetric analysis (TGA) results exhibited that the temperature at 5 mass% loss (T₅) increased from 277 °C to 310 °C for nanocomposite containing 2 mass% of DLDH, while T₅ for nanocomposite containing 2 mass% of ALDH increased to 320 °C, along with the more enhancement of char residue compared to the neat PAI. According to the tensile test results, with 5 mass% DLDH loading in the PAI matrix, the tensile strength increased from 51.6 to 70.8 MPa along with an increase in Young's modulus. Also the Young's modulus of PAI nanocomposite containing 5 mass% ALDH reduced from 1.95 to 0.81 GPa.     

Effect of poly(amid–imide)/Al2O3 hybrid with various ratios on the physicochemical properties of poly(vinyl alcohol) nanocomposites films

To study the effect of the various ratios of poly(amide–imide)/Al₂O₃ nanocomposites (PANC)s on the mechanical and thermal properties of nanocomposites films, poly(vinyl alcohol) (PVA)/PANCs based on various ratios of 2, 4, and 6 wt% were prepared and characterized. In the first step, the surface of alumina nanoparticles was treated with 15 wt% of biosafe diacid and consequently, about 10 wt% of these modified nanoparticles were loaded into the poly(amide–imide) matrix. Then, various contents of the obtained PANCs were incorporated into a PVA solution using a sonochemical treatment. The effects of PANC on the structure and morphology of PVA matrix were studied using powder X-ray diffraction, field emission scanning electron microscopy, transmission electron microscopy, Fourier transform infrared spectroscopy, atomic force microscopy (AFM), and thermal gravimetric analysis (TGA). The results show that the tensile strength and decomposition temperature were improved as the portion of PANC into PVA matrix are increased from 2 to 6 wt%. Also, AFM pictures of the fracture surfaces of PVA/PANCs showed a significantly rougher surface than the neat PVA.     

Microstructure and dynamic mechanical analysis of extruded layered silicate PVC nanocomposites

The nanostructure and dynamic mechanical properties of polyvinyl chloride (PVC) and the bentonite nanocomposites have been investigated. Nanocomposites with 5 wt% concentration of bentonite were prepared by melt extrusion followed by two‐roll‐milled processing. Atomic force microscopy (AFM) and wide‐angle X‐ray scattering (WAXS) were utilized to study the micro and nanostructure of the two‐roll‐milled sheets. The nanocomposites were compounded with two types of coupling agents: KZTPP® and Tamol 2001®. Optical microscopy showed that the materials remained optically transparent, i.e. they did not show evidence of nanoclay agglomeration. The WAXS patterns of PVC‐bentonite‐KZTPP nanocomposite were anisotropic, suggesting flow‐induced preferred orientation of the nanoplates. Moreover, the 001 reflection of the bentonite was shifted toward smaller angles, suggesting that the nanoplates were intercalated by the macromolecules. On the other hand, the WAXS patterns of PVC‐bentonite‐Tamol 2001 nanocomposite remained isotropic and did not show evidence of bentonite, suggesting exfoliation of the nanoplates. The nanocomposites showed an increase in glass transition temperature T_g, with the sequence T_g,PVC < T_g,KZTPP < T_{g,Tamol 2001}. Moreover, dynamic mechanical analysis (DMA) showed an increase in mechanical moduli and activation energy (and a decrease in the intensity of the mechanical damping Tan δ) following the same sequence. Interestingly, the improvement in mechanical moduli became more pronounced above the glass transition temperature. Copyright © 2008 John Wiley & Sons, Ltd.     

Development of novel cardo‐containing phenylethynyl‐terminated polyimide with high thermal properties

A phenylethynyl‐terminated reactive diluent [Card‐4‐phenylethynylphthalic anhydride (PEPA)], which contained fluorenyl cardo structures, was successfully synthesized and used as a modifier for flexible phenylethynyl‐terminated imide oligomer (PEI‐PEPA). The chemical structure, crosslink characterization, molecular weights, and thermal properties of the products were characterized. The imide systems with addition of 10, 20, 30, and 40 wt% Card‐PEPA to PEI‐PEPA (PEI‐PEPA‐Card) and their cured resin systems were prepared. The thermal curing behaviors of imide systems at different heating rates were analyzed by using differential scanning calorimetry. Thermal properties such as glass transition temperature (T_g) and char yield at 800°C of the resultant resin systems were studied by differential scanning calorimetry, dynamic mechanical analysis, and thermogravimetric analysis. The rheological properties were also investigated using a dynamic rheometry. These properties were found to be outstanding compared with pure PEI‐PEPA. The uncured imide systems exhibited lower T_g and lower isothermal viscosity with addition of Card‐PEPA. Furthermore, the T_g and char yield of the cured resin systems increased with addition of Card‐PEPA. The cured resin systems containing 40 wt% Card‐PEPA exhibited the highest T_g of 359°C and char yield at 800°C of 66.5%. Copyright © 2016 John Wiley & Sons, Ltd.     

In situ preparation of ultrafine Ru nanocatalyst supported on nitrogen-doped layered double hydroxide by nitrogen glow discharge plasma for catalytic hydrogenation of N-ethylcarbazole

Ultrafine Ru nanoparticles (RuNPs) supported on nitrogen-doped layered double hydroxide (Ru/LDH) were in situ prepared by nitrogen glow discharge plasma (nGDP) without adding any chemical reducing agents or stabilizers. The as-synthesized Ru/LDH catalysts were characterized by X-ray diffraction, X-ray photoelectron spectroscopy, transmission electron microscopy, and Fourier transform infrared spectroscopy. During treatment with nGDP, the reduction of Ru³⁺ and nitrogen doping were carried out simultaneously. The resulting RuNPs has a narrow particle size distribution of 1.41–2.61 nm, an ultrafine average particle size of 1.86 nm, and were uniformly dispersed on nitrogen-doped LDH. The complexation of RuNPs and O/N-containing functional groups on LDH improve the catalytic activity and stability of Ru/LDH. The catalyst exhibited excellent properties for the hydrogenation reaction of N-ethylcarbazole (NEC). The conversion of NEC and the selectivity of 12H-NEC were 100% and 99.06% for 1 hr at 120°C and 6 MPa H₂, respectively. The mass hydrogen storage capacity was 5.78 wt%. The apparent activation energy was 35.78 kJ/mol.     

Structure and thermal behaviors of poly(vinyl alcohol)/surfactant composites: Investigation of molecular interaction and mechanism

Poly(vinyl alcohol) (PVA) is a promising biocompatible polymer, whose applicability is limited by its narrow processing window. Here, we adopted a facile approach to broaden the processing windows of PVA based on phosphoric ester of poly(ethylene oxide) (10) nonylphenyl (NP‐10P). Thermal analysis shows that both the melting temperature (T_m) and the glass transition temperature (T_g) of PVA decrease noticeably as NP‐10P content increases, indicating good miscibility of NP‐10P with PVA. The thermal degradation kinetics suggests composites display excellent thermal stability compared with neat PVA. The pyrolysis mechanism of PVA before and after modification with NP‐10P varies from chain unzipping degradation followed by chain random scission to chain random scission. The processing window of PVA is broadened from 9°C to 98°C with low content NP‐10P (5 wt%). Moreover, the composites maintain significant mechanical performance and transparency. This work provides an environmentally friendly and economical method to improve the possibility of thermal melt processing for PVA.     

Synthesis and Characterization of PE-g-MA／MgAI-LDH Exfoliation Nanocomposite via Solution Intercalation

An organo‐modified MgAl‐layered double hydroxide (OMgAl‐LDH) was successfully exfoliated in the xylene solution of polyethylene‐grafted‐maleic anhydride (PE‐g‐MA) under re‐fluxing condition. A PE‐g‐MA/MgAl‐LDH exfoliation nanocomposite was formed after the precipitation of PE‐g‐MA from the dispersion system. The structure and thermal property of the PE‐g‐MA/MgAl‐LDH exfoliation nanocomposite were characterized by X‐ray diffraction (XRD), transmission electron microscopy (TEM), and thermogravimetry analysis (TGA). The disappearance of d₀₀₁ XRD peak of OMgAl‐LDH at 20 = 3.2° suggests that the MgAl hydroxide sheets are exfoliated in the nanocomposite. The TEM image shows that the MgAl hydroxide sheets of less than 70 nm in length or width are exfoliated and dispersed disorderly in PE‐g‐MA matrix. TGA profiles indicate that the PE‐g‐MA/MgAl‐LDH nanocomposite with 5 wt% OMgAl‐LDH loading shows a faster charring process in temperature range from 210 to 390 °C and a greater thermal stability beyond 390 °C than PE‐g‐MA does. The decomposition temperature of the nanocomposite is 25 °C higher than that of PE‐g‐MA as measured at 50% weight loss. The PE‐g‐MA/MgAl‐LDH nanocomposite is promising for application of flame‐retardant polymeric materials.     

Measurement of size‐dependent glass transition temperature in electrospun polymer fibers using AFM nanomechanical testing

The glass transition temperature (T_g) of individual electrospun polymer polyvinyl alcohol fibers of varying diameter was measured using atomic force microscopy (AFM) based nanomechanical thermal analysis. Indentation and bending of individual electrospun fibers using AFM allowed the calculation of the elastic modulus of the polyvinyl alcohol (PVA) fibers across a range of different temperatures. The elastic modulus of electrospun PVA fibers was observed to decrease significantly when passing through T_g, which allowed accurate determination of T_g. The T_g of electrospun PVA fibers was shown to decrease for smaller fiber diameters especially for fiber diameters below 250 nm. This size‐dependent glass transition behavior of electrospun PVA fibers is indicated as being due to polymer chain confinement. © 2011 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys, 2011     

Thermal properties of poly(methyl methacrylate-co-butyl acrylate-co-acrylic acid) modified with divinyl benzene and vinyltrimethoxysilane

The effect of butyl acrylate (BA), divinyl benzene (DVB) and vinyltrimethoxysilane (TMVS) on the thermal properties of poly(methyl methacrylate-co-butyl acrylate-co-acrylic acid) was investigated. Glass transition temperature (T_g), melting temperature (T_m) and specific heat capacity of the copolymers were investigated using Differential Scanning Calorimetry. Thermal stability of the copolymers which is associated with the degradation temperature (T_d) was studied by Thermogravimetric Analysis. Polyacrylates with T_g ranges between -19°Cand 19°C were obtained. With the incorporation of >7 wt% of DVB, the T_g of the copolymer increases from about ?17°C to ?10°C even though they have not undergone UV irradiation. Gel content results prove that crosslinking has occurred in the copolymers. With increasing amount of TMVS from 0 wt% to 7 wt%, the T_m of the copolymers prepared at acidic pH is about 40-60°C higher than that at the alkaline pH. However, the addition of TMVS gives no significant effect to the T_g and T_d of the copolymer films. The thermal stability of the copolymer has improved with increasing amount of BA and DVB, with DVB being more effective. The highest T_d of 425°C with 8% of DVB has been obtained. Consequently, a polyacrylate copolymer with a T_g of about ?13°C, a T_m of 170 °C and a T_d of about 424°C has been successfully synthesized. Hence, the soft polyacrylate with its relatively high T_m and T_d could serve as a superb material especially to be applied in the areas that require high melting temperature and good thermal stability.     

Tri(3-alkoxyl-3-oxopropyl) phosphine oxides derived from PH3 tail gas as a novel phosphorus-containing plasticizer for polylactide

Preparing a polylactide (PLA)/plasticizer system has been regarded as an effective solution to improve the ductility of brittle PLA. In this reach, a novel type of alkyl phosphine oxides consisting of three aliphatic ester substituents was prepared from PH₃ tail gas, and its potential to be employed as a PLA plasticizer was studied. Differential scanning calorimeter tests confirmed that the newly-prepared plasticizer decreased the T_g of PLA (28 wt% plasticizer) from 52°C (neat PLA) to 11°C, and increased the elongation at break from 11% (neat PLA) to 271% (plasticized PLA). X-ray diffraction results showed that the crystallization degree of PLA (28 wt% plasticizer) increased from 0.12% of neat PLA to 14.04%, while Young's modulus of PLA remained as high as 121.3 MPa, which was much higher than that of the PLA/citrate ester systems with same plasticizer content. These novel phosphorus-containing plasticizers exhibited excellent thermal stability and a weight-loss of the system no more than 2.5% at 180°C; therefore, no unpleasant volatiles were released during processing. In contrast, the weight loss of the PLA/citrate system was as high as 10.8% at 180°C, forming heavy fog with an unpleasant smell during thermal mixing. Scanning electron microscopy was employed to observe the microstructure of the PLA/plasticizer systems, which indicated that the carboxylic butyl ester-containing phosphine oxides was compatible with PLA matrix.     

Poly(vinyl alcohol)/melamine phosphate composites prepared through thermal processing: thermal stability and flame retardancy

Poly(vinyl alcohol)/melamine phosphate composites (PVA/MP) as a novel halogen‐free, flame‐retardant foam matrix were prepared through thermal processing, and then their thermal stability and flame retardancy were investigated by thermo‐gravimetric analysis, micro‐scale combustion calorimeter, cone calorimeter, vertical burning test, and limiting oxygen index (LOI) test. It was found that the thermal stability and combustion properties of the PVA/MP composites could be influenced by the addition of MP. Compared with the control PVA sample (B‐PVA), in the PVA/MP (75/25) composites, the temperature at 5% mass loss (T_5%) decreased about 10°C, the residual chars at 600°C increased by nearly 27%, the temperature at the maximum peak heat release rate (T_P) shifted from 292°C to 452°C, and the total heat released and the heat release capacity (HRC) decreased by 28% and 14%, respectively. Moreover, the PVA/MP composites could reach LOI value up to 35% and UL94 classification V‐0, showing good flame retardancy. At the same time, both Fourier transform infrared and X‐ray photoelectron spectroscopy spectra of the residual chars from the PVA/MP composites demonstrated that the catalytic effect of MP on the dehydration and decarboxylation reactions of PVA, and the chemical reactivity of MP during the chars‐forming reactions could be used to account for the changed thermal stability and flame retardancy of the PVA/MP composites. Copyright © 2012 John Wiley & Sons, Ltd.     

Organic–inorganic nanocomposites prepared from fluoro-aramid and silica

Fluoro-aramid-based sol/gel-derived nanocomposites were synthesized by condensing a mixture of 4,4′-(hexafluoro-isopropylidene)dianiline and 1,3-phenylenediamine with terephthaloylchloride (TPC) in dimethylacetamide. TPC was added in slight excess to produce amide chains with carbonyl chloride end groups and then replaced with alkoxy groups using aminophenyltrimethoxysilane to develop bonding with the silica network. Mechanical, dynamic mechanical thermal, water absorption and morphological measurements were carried out on the thin hybrid films. Increase in the tensile strength and modulus was observed as compared to pristine polyamide. The thermal decomposition temperature was found in the range of 400–500 °C. The water absorption was found to be reduced with higher silica content. The glass transition temperature and the storage moduli increased with increasing silica concentration. The maximum increase in the T _g value (345 °C) was observed with 20 wt% silica. Scanning electron microscopy revealed the uniform distribution of silica in the matrix with an average particle size ranging from 8 to 50 nm.     

Viscoelastic behaviors and molecular motions of highly syndiotactic poly(vinyl alcohol) fibers

The viscoelastic behavior and molecular motion of highly syndiotactic poly(vinyl alcohol) (S‐PVA) fibers with a dyad syndiotacticity (r) of 69% were studied by dynamic mechanical thermal analysis and wide‐angle X‐ray diffraction and compared with those of atactic poly(vinyl alcohol) (A‐PVA) fibers with r = 54%. The β_c dispersion, based on the molecular motion of the chain molecules in the crystalline regions, was observed for A‐PVA around 120–140 °C, and the only primary (α_c) dispersion was observed for S‐PVA around 180 °C. The thermal expansion coefficients for the a and c axes of the A‐PVA crystal changed discontinuously around 120 °C, which corresponded to the β_c dispersion. For S‐PVA, the coefficient for the (002) plane changed discontinuously around 100 °C, similarly to A‐PVA, but that for the (100) plane remained unchanged between 20 and 220 °C. These results showed that the intermolecular hydrogen bonding of S‐PVA was stronger in the direction of the a axis than in the other directions, suppressing the β_c dispersion. The storage modulus and thermal expansion coefficient of the (020) plane (molecular axis) of S‐PVA decreased markedly around 180 °C, and this indicated that the α_c dispersion was due to the torsional motion of the molecular chains in the crystalline regions. © 2004 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 42: 800–808, 2004     

Synthesis of a random copolymer and its compatibility for thermotropic liquid crystalline polymer/poly(ether ether ketone) blends

A random copolymer (RCP) containing poly(ether ether ketone) (PEEK) and thermotropic liquid crystalline polymer (TLCP) segments was synthesized. Its chemical structure and liquid crystalline properties were characterized by FT‐IR, differential scanning calorimetry (DSC) and polar light microscopy (PLM) respectively. A single glass transition temperature (T_g) at 134.0°C, a melting temperature (T_m) at 282.0°C and a temperature of ignition (T_i) at 331.3°C can be observed. Blends of PEEK and TLCP with and without RCP as compatibilizer were prepared by extrusion and the effect of RCP on the thermal properties, dynamic mechanical properties, morphology and static tensile mechanical properties of blends was investigated by means of DSC, dynamic mechanical analysis (DMA), scanning electron microscopy (SEM), etc. Dynamic mechanical measurements indicated that there appeared to be only a single tan δ peak resulting from the glass transition of the PEEK‐rich phase and the T_g value shifted towards higher temperature due to the presence of compatibilizer, as suggested partial compatibility. Morphological investigations showed that the addition of RCP to binary blends reduced the dispersed phase size and improved the interfacial adhesion between the two phases. The ternary compatibilized blends showed enhanced tensile modulus compared to their binary blends without RCP. The strain at break decreased for the ternary blends due to embrittlement of the matrix by the incorporation of some RCP to the matrix phase. Copyright © 2007 John Wiley & Sons, Ltd.     

The potential use of electrospun polylactic acid nanofibers as alternative reinforcements in an epoxy composite system

This pilot study elaborates the development of novel epoxy/electrospun polylactic acid (PLA) nanofiber composites at the fiber contents of 3, 5, and 10 wt % to evaluate their mechanical and thermal properties using flexural tests and differential scanning calorimetry (DSC). The flexural moduli of composites increase remarkably by 50.8 and 24.0% for 5 and 10 wt % fiber contents, respectively, relative to that of neat epoxy. Furthermore, a similar trend is also shown for corresponding flexural strengths being enhanced by 31.6 and 4.8%. Fractured surface morphology with scanning electron microscopy (SEM) confirms a full permeation of cured epoxy matrix into nanofiber structures and existence of nondestructive fibrous networks inside large void cavities. The glass transition temperature (T_g) of composites increases up to 54–60 °C due to embedded electrospun nanofibers compared to 50 °C for that of epoxy, indicating that fibrous networks may further restrict the intermolecular mobility of matrix in thermal effects. © 2014 Wiley Periodicals, Inc. J. Polym. Sci., Part B: Polym. Phys. 2014 , 52, 618–623     

Application of CuO nanoparticles modified with vitamin B1 for the production of poly(vinyl alcohol)/CuO nanocomposite films with enhanced optical,thermal and mechanical properties

In this Investigation, the CuO nanoparticles (NPs) were treated by vitamin B₁ as a biomolecule modifier. The CuO NPs were used as an appropriate filler for fabrication of poly(vinyl alcohol) (PVA) nanocomposites (NCs). Then, NCs with various ratios (3, 5, and 7wt%) of modified CuO were fabricated under ultrasonic irradiation and their properties were compared with pure PVA. Several techniques were used for characterization of NCs. Field emission scanning electron microscopy and transmission electron microscopy analysis indicated that NPs have proper compatibility with the PVA matrix. Thermal gravimetric analysis results confirmed that NCs displayed higher thermal stability than neat PVA. Also, the addition of the NPs into the PVA matrix improved the optical and mechanical behaviors. Finally, the contact angle measurements verified that the hydrophilicity decreased for different ratios of modified NPs loaded in the polymer matrix. Copyright © 2017 John Wiley & Sons, Ltd.     

Thermal analysis and microscopical characterization of cholesterol in gallstones

Summary Cholesterol constitutes the major component of most gallstones. It was identified and determined in gallstones by thermal analysis technique (DSC and TG-DTA), mainly by the use of the melting temperature (T_onset=145°C and T_max=149°C) and by DTG peak decomposition (T_max=364°C). Cholesterol anhydrous (ChA), which showed endothermic polymorphic peak, T_max=40°C, without mass loss, was differentiated from cholesterol monohydrate (ChH), which showed a broad endothermic peak, T_max=59°C, attributed to loss of water of crystallization (theoretical 4.45%). Morphological studies of gallstones were performed by optical microscopy and scanning electron microscopy (SEM). The stones consisted of a pigmented core with a variably-sized irregular central cavity, surrounded by a radially arranged deposits of plate-like ChH. The outer part of the stones showed ChA crystal arborescences. X-ray microanalysis gave a typical spectrum rich in C and O, and in some instances the presence of P, which was attributed to the presence of phospholipids. CaCO₃ was easily characterized by TG with the use of DTG decomposition peak at 674°C.     

Surface modification of cellulose nanowhiskers for application in thermosetting epoxy polymers

Cellulose nanowhiskers (CNWs) were chemically modified with dodecenyl succinic anhydride to obtain hydrophobic CNWs called DCNWs. Surface modification was confirmed by infrared spectroscopy, transmission electron microscopy, and X-ray diffraction. The surface substitution degree determined by X-ray photoelectron spectroscopy was 0.30. Nanocomposites were prepared by incorporating different amounts of DCNWs pre-dispersed in a small amount of acetone into an epoxy matrix. Scanning electron microscope demonstrated that DCNWs dispersed well in the epoxy matrix. A strong interaction was proved between the DCNWs and epoxy matrix, as results of which the nanocomposites exhibited an obvious increase in T _g by about 30 °C, simultaneous increases in tensile strength, Young’s modulus, and strain at break; and an improvement in the hydrothermal properties. Compared with the neat epoxy, the nanocomposite containing 3.5 wt% of DCNWs exhibited an increase in tensile strength by 82 %, Young’s modulus by 21 %, and a strain at break by 198 %.     

Investigation of structural,rheological and thermal properties of PMMA/ONi-Al LDH nanocomposites synthesized <Emphasis Type="Italic">via</Emphasis> solvent blending method: Effect of LDH loading

This article addresses the synthesis of organically tailored Ni-Al layered double hydroxide (ONi-Al LDH) and its use in the fabrication of exfoliated poly(methyl methacrylate) (PMMA) nanocomposites. The pristine Ni-Al LDH was initially synthesized by co-precipitation method and subsequently modified using sodium dodecyl sulfate to obtain ONi-Al LDH. Nanocomposites of PMMA containing various amounts of modified Ni-Al LDH (3 wt%-7 wt%) were synthesized via solvent blending method to investigate the influence of LDH content on the properties of PMMA matrix. Several characterization methods such as X-ray diffraction (XRD), transmission electron microscopy (TEM), Fourier transform infrared spectroscopy (FTIR), rheological analysis, differential scanning calorimetry (DSC) and thermo gravimetric analysis (TGA), were employed to examine the structural, viscoelastic and thermal properties of PMMA/OLDH nanocomposites. The results of XRD and TEM examination confirm the formation of partially exfoliated PMMA/OLDH nanocomposites. The FTIR results elucidate that the characteristic bands for both pure PMMA and modified LDH are present in the spectra of PMMA/OLDH nanocomposites. Rheological analyses were carried out to examine the adhesion between polymer matrix and fillers present in the nanocomposite sample. The TGA data indicate that the PMMA nanocomposites exhibit higher thermal stability when compared to pure PMMA. The thermal decomposition temperature of PMMA/OLDH nanocomposites increases by 28 K compared to that of pure PMMA at 15% weight loss as a point of reference. In comparison with pure PMMA, the PMMA nanocomposite containing 7 wt% LDH demonstrates improved glass transition temperature (T _g) of around 3 K. The activation energy (E _a), reaction orders (n) and reaction mechanism of thermal degradation of PMMA/OLDH nanocomposites were evaluated using different kinetic models. Water uptake capacity of the PMMA/OLDH nanocomposites is less than that of the pure PMMA.     

Aqueous solution behavior of comb‐shaped poly(2‐ethyl‐2‐oxazoline)

A series of comb polymers consisting of a methacrylate backbone and poly(2‐ethyl‐2‐oxazoline) (PEtOx) side chains was synthesized by a combination of cationic ring‐opening polymerization and reversible addition–fragmentation chain transfer polymerization. Small‐angle neutron scattering (SANS) studies revealed a transition from an ellipsoidal to a cylindrical conformation in D₂O around a backbone degree of polymerization of 30. Comb‐shaped PEtOx has lowered T_g values but a similar elution behavior in liquid chromatography under critical conditions in comparison to its linear analog was observed. The lower critical solution temperature behavior of the polymers was investigated by turbidimetry, dynamic light scattering, transmission electron microscopy, and SANS revealing decreasing T_cp in aqueous solution with increasing molar mass, the presence of very few aggregated structures below T_cp, a contraction of the macromolecules at temperatures 5 °C above T_cp but no severe conformational change of the cylindrical structure. In addition, the phase diagram including cloud point and coexistence curve was developed showing an LCST of 75 °C of the binary mixture poly[oligo(2‐ethyl‐2‐oxazoline)methacrylate]/water. © 2012 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem, 2013