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Photon correlation spectroscopy has been successfully employed to study the dynamics of the local segmental and sub-Rouse motion of a monodisperse polyisobutylene near and above the glass transition temperature. The separation between the maxima of the two peaks corresponding to these two viscoelastic mechanisms is obtained for several temperatures. The temperature dependence of the local segmental...
Using a relation derived from the blob model we obtain an equation giving the Θ temperature of the polymers. This equation predicts for the star shaped polymers a decrease or an increase in their Θ temperature compared with the Θ temperature of the corresponding linear polymers. The value of the Θ temperature of star polymers is tightly related to their degree of branching. The predictions of this...
In this paper a synthetic procedure is described towards a new class of methacrylated dextrans which are sensitive to hydrolysis. These methacrylated dextrans, which can be used for the development of biodegradable hydrogels, were obtained by grafting L-lactide onto 2-hydroxyethyl methacrylate (HEMA), followed by activation of the terminal hydroxyl group with N,N -carbonyldiimidazole (CDI), yielding...
Polyampholyte microgels have been synthesized by copolymerizing the anionic monomer sodium 2-acrylamido-2-methylpropanesulfonate (NaAMPS), the cationic monomer (2-(methacryloyloxy)ethyl)trimethylammonium chloride (MADQUAT), and a crosslinking monomer N,N -methylenebisacrylamide (BA), using an inverse microemulsion route. The swelling properties of so-called balanced microgel particles (i.e....
Brush-like graft polylactide (PLA) and poly(lactide-co-glycolide) (PLG) containing water soluble charged dextrans: dextran sulphate sodium (DSS) and diethylaminoethyl dextran chloride (DEAED) as backbones were synthesized in a bulk polymerization reaction using stannous octoate as catalyst. The polymers were characterized by n.m.r., g.p.c., LS, intrinsic viscosity measurement and d.s.c. methods....
Blends of poly(3-hydroxybutyrate) (PHB)/poly(methylene oxide) (POM) were prepared by melt mixing and subsequent compression moulding. Crystallization, thermal behaviour, morphology and mechanical properties of the blends were studied by using differential scanning calorimetry, optical and scanning electron microscopy, and dynamic-mechanical analysis. The immiscibility of the two polymers in the liquid...
The interactions between acrylamide-acrylic acid copolymers and alkalinoearth cations were studied by many different techniques, as functions of various parameters: composition of the copolymer and distribution of the acrylic units along the chain; pH; temperature; ionic strength. In a first step, the phase diagrams were established and reveal ranges of polymer and salt concentrations where phase...
The photoinitiated polymerization of dimethacrylate oligomer with 2,2-dimethyl-2-hydroxy acetophenone (Darocur 1173) as radical photoinitiator was studied by using isothermal photocalorimetry. The effect of temperature, light intensity and photoinitiator concentration on reaction was investigated. The maximum conversion was obtained at temperature near 90°C. This temperature is above the glass...
Low density polyethylene (LDPE) and high density polyethylene (HDPE) were plasma-treated with N 2 and O 2 plasma. The wettability and polar component of surface free energy of plasma-treated polyethylene were investigated by contact angle measurement. The concentration of functional groups formed by plasma treatment such as hydroxyl and carbonyl groups was measured using attenuated...
The kinetics of catalysed and uncatalysed acidolysis between hydroquinone diacetate-terephthalic acid (HT), hydroquinone diacetate-isophthalic acid (HI) and resorcinol diacetate-terephthalic acid (RT) were investigated at 280, 290, 300, 310 and 320°C. Two kinetic regimes were observed in the rate law plots. Kinetic behaviour in the two regimes differed with the system. Simple second order rate...
Chitin/poly(glycidyl methacrylate) (PGMA) composites were synthesized via bulk polymerization in a gel state of chitin impregnated with reactive GMA monomer. The thermal transition behaviour and phase structure of the chitin/PGMA composites were characterized by differential scanning calorimetry (d.s.c.), dynamic mechanical analysis (d.m.a.), and solid-state 13 C n.m.r. spectroscopy...
A series of novel perfluorononenyloxy group containing aromatic polyamides were synthesized by direct polycondensation of 5-(perfluorononenyloxy)isophthalic acid (I) with various aromatic diamines in N-methyl-2-pyrrolidone (NMP) containing lithium chloride. In this process, triphenyl phosphite and pyridine were used as condensing agents. All the aromatic polyamides were amorphous and readily soluble...
Poly(methyl methacrylate-co-butyl acrylate) latex particles were synthesized by both seeded and unseeded semicontinuous emulsion copolymerization processes. Particle size and surface charge densities were characterized by TEM and potentiometric and conductimetric titrations, respectively. The electrophoretic mobilities of the latexes were studied at different ionic strength and constant pH and then...
Catalytic chain transfer polymerization (CCTP) of methacrylates is an efficient method to produce low molecular weight poly(methacrylates). The mechanism is such that the products each have a terminal vinyl group which is then available for subsequent further reaction. This study involves the use of matrix assisted laser/desorption ionization time-of-flight mass spectrometry (MALDI TOF MS) to investigate...
Structural characterization studies using Raman and i.r. spectroscopy and extended X-ray absorption fine structure (EXAFS) on the (PEO) n [(ZnBr 2 ) 1-x (LiBr) x ] system (n = 20, 40; x = 0-0.8) are reported. Raman spectroscopy reveals that the ionic species present in the complex depend on the Zn:Li ratio and the ether oxygen to metal ion ratio. With increasing...
A super-tough polycarbonate (PC) blend was obtained by using epoxidized ethylene propylene diene (eEPDM) rubber as modifier. The notched Izod impact strength of PC/eEPDM (96/4) blend shows a great improvement, with a value about 25 times of that of pure PC. Finely and homogeneously dispersed rubber particles (0.2-0.8 μm) in the PC matrix indicated good adhesion between the eEPDM rubber phase and...
New results of molecular modelling investigations on the transport of different small molecules in polyimides and polysiloxanes are discussed. The transition state Gusev-Suter Monte Carlo method reveals a reasonable coincidence between simulated and measured diffusivity and solubility values for the polyimides. A comparison between simulation data obtained for flexible chain polymers like poly(dimethyl...
Reactive melt processing of polyethylene (PE) was accomplished at 170°C under the influence of two different doses (0.75 and 1.25 mmol per 100 g PE) of dicumyl peroxide (DCP). The effect of peroxide action on melt rheology of PE at 160, 180 and 190°C was studied by a constant shear rate plate and cone viscometer. Peroxide action led to establishment of a mild degree of crosslinkages in PE and hence...
A method for the ambient temperature curing of acrylic emulsions with epoxy resins has been developed. The results show that an acrylic resin can be effectively cured at room temperature through the addition of between 5 and 20 wt% of epoxy resin to the acrylic monomers. The resulting cured polymers have a degree of reticulation of the order of 75%. It is shown that the tensile strength, and water...
Analysis of the copolyesterification in bulk without any external catalyst at 205°C between o-phthalic anhydride, oleic acid and neopentyl glycol (2,2-dimethyl-1,3-propanediol) with a mole ratio ([-COOH]/[-OH])=0.70 has been carried out by high resolution 13 C and 1 H n.m.r. The different polymeric sequences and several monomeric structures formed during the copolyesterification...
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