The Infona portal uses cookies, i.e. strings of text saved by a browser on the user's device. The portal can access those files and use them to remember the user's data, such as their chosen settings (screen view, interface language, etc.), or their login data. By using the Infona portal the user accepts automatic saving and using this information for portal operation purposes. More information on the subject can be found in the Privacy Policy and Terms of Service. By closing this window the user confirms that they have read the information on cookie usage, and they accept the privacy policy and the way cookies are used by the portal. You can change the cookie settings in your browser.
When poly(d-lactide) (PDLA) is mixed with poly(l-lactide) (PLLA) of similar molecular weight and crystallized from the melt in ultrathin films (30 nm), hexagonal single crystals are obtained at the equimolar composition, and triangular single crystals at non-equimolar compositions. Here, stereocomplexes are formed by blending PDLA with a PLLA incorporated as the central block of a triblock copolymer...
Crystallization kinetics of poly (S-2-hydroxybutanoic acid) [P(S2HB)] and P(S2HB)/P (R2HB) stereocomplexes were investigated by in situ atomic force microscopy, polarized optical microscopy, and differential scanning calorimetry. For the homopolymer, an equilibrium melting temperature Tm° of 130.3 °C is obtained according to the Hoffman-Weeks method. In the case of thin films of 50 nm in thickness,...
Morphologies of ultrathin films (10–60 nm) of miscible poly(ε-caprolactone)/poly(vinyl chloride) (PCL/PVC) blends have been investigated under isothermal crystallization conditions by real time atomic force microscopy, and electron diffraction techniques. It was found that the morphology and growth rate of PCL/PVC blends strongly depend on the blend composition, crystallization temperature and film...
The simultaneous orientation of poly(1,4-butylene)succinate (PBS) and 4,4′-bis(2-benzoxazolyl)stilbene (BBS) or 2,5-bis(5-tert-butyl-benzoxazol-2-yl)thiophene (BBT) in PBS–BBS and PBS–BBT films was investigated during stretching at 80 °C, about 33 °C below the PBS melting temperature. The PBS orientation was first investigated using the 3430 cm −1 infrared band and its order parameter <P...
Linear and star-shape PGMAs were synthesized by atom transfer radical polymerization and then functionalized with four different amines by ring-opening addition. This resulted in the formation of polyglycerol-like polymers having both hydroxyl and amine moieties and different water-solubility. The water insoluble polymers could form pH-sensitive nanoassemblies, while the soluble derivatives efficiently...
The orientation of poly(ε-caprolactone) crystals in miscible poly(ε-caprolactone)/poly(vinyl chloride) (PCL/PVC) blends, melt crystallized under strain, has been studied by wide angle X-ray diffraction (WAXD). At low draw ratios or low PVC contents, all the observable (hk0) crystal reflections orient towards the meridional direction in WAXD patterns, indicating the presence of ring-fibre orientation...
The influence of minute amounts of residual tetrahydrofuran on the crystallization of ultrathin poly(ε-caprolactone) (PCL) films has been investigated in real-time by atomic force microscopy. Crystallizations were performed at 30°C, after melting at 64°C, for different periods of time; both the morphology and growth rate of the crystals were found to depend on the thermal history of the sample, i...
Deformation of polyethylene terephthalate, PET, was simulated using atomistic molecular dynamics using a Parrinello-Rahman constant-stress constant-temperature algorithm under periodic boundary conditions. The evolution in trans and gauche populations is in good agreement with experimental data reported in the literature: In the isotropic model, approximately 15% trans angles are found, and the trans...
The bonding of polystyrene (PS) surfaces below T g was investigated by two different fracture tests: the lap-shear joint method and the cantilever beam method. Adhesion energy values obtained by the two methods are in agreement and develop with (time) 1/2 , at temperatures as low as T g −16 °C. Even if the double cantilever method is the most common test found in the literature...
The effect of thermal history on the orientation and relaxation behavior of blends of polystyrene with poly(vinyl methyl ether) (PS/PVME) has been studied using polarization modulation infrared linear dichroism (PM-IRLD) and differential scanning calorimetry (DSC). DSC shows that miscible PS/PVME blends containing 70% of PS can be physically aged at temperatures above their mean glass transition temperature...
The phase behavior of ternary blends made of poly(epichlorohydrin) (PECH), poly(vinyl acetate) (PVAc) and poly(methyl methacrylate) (PMMA) has been investigated by differential scanning calorimetry (DSC) and dynamic mechanical thermal analysis (DMTA). DMTA measurements have been shown to be more sensitive than DSC for the detection of a second phase, for the determination of the composition of each...
Healing of interfaces of amorphous and semi-crystalline poly(ethylene terephthalate) (PET) was carried out above and below the (bulk) glass transition temperature (T g ) of the samples (two amorphous and two semi-crystalline polymers of different molecular weights). The lap-shear strength of the amorphous/amorphous interface was found to develop without discontinuity in the vicinity of the...
Poly(ethylene terephthalate) (PET) has been uniaxially stretched at different draw ratios and draw rates above its glass transition temperature, in the 80–105°C temperature range. Molecular orientation and relaxation have been followed by birefringence. A decrease in temperature reduces the mobility of the oriented chains resulting in a slow relaxation while an increase in stretching rate results...
The influence of thermal history on the stability of stereocomplexes of isotactic and syndiotactic poly(methyl methacrylate) PMMA was investigated using differential scanning calorimetry. It was found that a prolonged annealing of the stereocomplex not only increases its crystallinity but also leads to the appearance of another, yet rather small, endotherm with a maximum located close to the beginning...
Molecular orientation and mechanical properties of miscible poly(styrene)/poly(vinyl methyl ether) (PS/PVME) blends were compared with those of heterogeneous PS/PVME blends prepared above their temperature of phase separation. The second moment of the orientation function and the Young's modulus of the heterogeneous systems were found to be higher than those of the corresponding miscible compositions...
Wide-angle X-ray diffraction measurements of the orientation distribution of (hkl) crystal planes give values of some of the P n (cos χ ) c coefficients, characterizing the orientation of the molecular chains, which disagree with those obtained from hk0 or 00l reflections. In this present article, a calculation method is proposed for obtaining reliable P n (cos...
Set the date range to filter the displayed results. You can set a starting date, ending date or both. You can enter the dates manually or choose them from the calendar.