Search results for "Monomer"
showing 10 items of 857 documents
Mechanism of Anionic Polymerization of (Meth)acrylates in the Presence of Aluminum Alkyls, 6. Polymerization of Primary and Tertiary Acrylates
1998
The kinetics of the polymerization of n-butyl acrylate initiated by lithiated ester enolates in the presence of aluminum alkyls was investigated in toluene and in toluene/Lewis base mixed solvents at −78 °C. In pure toluene, curved time−conversion plots, incomplete monomer conversion, and broad molecular weight distributions (Mw/Mn ≈ 2) are observedin the absence of aluminum alkyls the molecular weight distributions are significantly broader (Mw/Mn > 14). High monomer conversions and narrower molecular weight distributions (Mw/Mn ≈ 1.5) are obtained when using Lewis bases (e.g., methyl pivalate) as cosolvents. The polymerization of tert-butyl acrylate rapidly reaches full monomer conversion…
Die kationische ɛ-caprolactam-polymerisation. IV. Isolierung und strukturermittlung der oligomeren als beitrag zur aufklärung des polymerisationsmech…
1966
Molekulareinheitliche Oligomere von Polykondensations- und Polyadditionsreaktionen konnen zur Aufklarung von Struktur und Bildungsmechanismus der Polymeren dienen. Auf diesem Wege wird der fruher vorgeschlagene Mechanismus der kationischen Lactampolymerisation mit wasserfreien Sauren erhartet, der in einer Acylierung des Lactams durch Lactamsalz unter Bildung von Aminoacyllactamsalz und nachfolgendem Kettenwachstum durch Addition weiterer Lactammolekule an die entstandene und immer wieder neu gebildete Ammonium-Endgruppe besteht. Dazu werden aus Caprolactam und Chlorwasserstoff als Initiator unter geeigneten Bedingungen Oligomerengemische gewonnen und elektrophoretisch aufgetrennt. Mikropra…
A computational model of postprandial adipose tissue lipid metabolism derived using human arteriovenous stable isotope tracer data
2019
Given the association of disturbances in non-esterified fatty acid (NEFA) metabolism with the development of Type 2 Diabetes and Non-Alcoholic Fatty Liver Disease, computational models of glucose-insulin dynamics have been extended to account for the interplay with NEFA. In this study, we use arteriovenous measurement across the subcutaneous adipose tissue during a mixed meal challenge test to evaluate the performance and underlying assumptions of three existing models of adipose tissue metabolism and construct a new, refined model of adipose tissue metabolism. Our model introduces new terms, explicitly accounting for the conversion of glucose to glyceraldehye-3-phosphate, the postprandial …
Expression of nm23 in gastric carcinoma: association with tumor progression and poor prognosis.
1998
BACKGROUND Expression of nm23 has been shown to be inversely correlated with the metastatic potential of several human cancers. In the current study, the expression and prognostic impact of nm23 was immunohistochemically studied in 413 curatively resected gastric carcinomas. METHODS Tumor sections of the 413 gastric carcinomas were stained with a polyclonal antibody that was raised against the nm23-H1/NDP kinase A, which is identical to the nm23-H1 gene product. RESULTS Expression of nm23 was detected in 84.5% (n = 349) of all tumors, in the majority of cases (71.2%) causing a homogeneous staining reaction in more than 75% of tumor cells. Expression of nm23 was positively correlated with th…
Early stage human colorectal cancer: prognostic value of nm23-H1 protein overexpression
1997
Nm23 gene codifies for a nucleoside diphosphate kinase allowing the intracellular transduction of the signals. In colorectal cancer nm23 protein expression seems related to the progression of the disease. By immunohistochemistry we have studied the intracytoplasmatic nm23 H1 protein expression in 20 patients affected by colorectal cancer at initial stage. In 12 cases it resulted elevated and in four the disease recurred. The overexpression was not correlated with other prognostic factors. Nm23 H1-positive patients affected by colorectal cancer at initial stage could be considered at risk for disease recurrence and included in a more frequent follow-up protocol.
Variable phenotypic expression of chylomicron retention disease in a kindred carrying a mutation of the Sara2 gene
2010
Chylomicron retention disease is a recessive inherited disorder characterized by fat malabsorption and steatorrhea and is associated with failure to thrive in infancy. We describe a kindred carrying a mutation of Sara2 gene causing a chylomicron retention phenotype. The proband was a 5-month-old baby, born of consanguineous, apparently healthy parents from Morocco, with failure to thrive. There was a large quantity of fats in feces and malabsorption of fat-soluble vitamins. Intestinal biopsies showed a diffused enterocyte vacuolization with large cytosolic lipid droplets. Chylomicron retention disease or Anderson disease was hypothesized, and the Sara2 gene was analyzed by direct sequencing…
Dual emission of a bis(pyrene)-functionalized, perbenzylated beta-cyclodextrin
2008
A bis(pyrene)-functionalized β-cyclodextrin (1) has been prepared in two steps from perbenzylated β-cyclodextrin. This compound shows dual emission properties, which arise from the pyrenyl chromophores. Upon excitation of 1 at 355 nm, monomer blue fluorescence (386, 407 and 428 nm) is observed in DMSO solution, whereas excimer green fluorescence (477 nm) is seen upon addition of ≥20 vol% water in DMSO. This suggests that modified β-cyclodextrin 1 changes its shape in response to the environment. The sensing properties of 1 towards carboxylic acids and alcohols were investigated in H2O–DMSO (80 : 20 v/v). Monomer fluorescence is restored selectively by medium length normal carboxylic acids, …
Linear chain surfactants at a planar interface: a comparative Monte Carlo study of several lattice models
1993
Linear chain surfactants in a densely packed arrangement (such as alkane chains in lipid monolayers in the “uniform tilt” structures) are described by a crude coarse-grained model where the endgroups grafted on the interface form a regular lattice and the chains are described by the bond fluctuation model with chains containing N = 4 effective monomers only. Square-well interactions between the monomers are studied for both the attractive and repulsive case for three choices of the interaction range. None of these models exhibits a structure with uniform tilt. For attractive interactions the last bond has a strong tendency to fold back thus leading to a very high density close to the interf…
Mechanism of anionic polymerization of (meth)acrylates in the presence of aluminium alkyls, 1. 13C NMR studies of model compounds in toluene
1994
The bimetallic ate complex [(CH 3 ) 2 C=C(OEt)(O - AlR 3 )]Li + is regarded to be the model of the active centre of the polymerization of methyl methacrylate in the presence of aluminium alkyls. This complex is detectable by 13 C NMR up to 273 K. At ambient temperature irreversible decomposition takes place. Apart from the formation of the ate complex, excess aluminium chloride coordinates to the ester carbonyl groups of both the monomer and the polymer chain
Selective adsorption of oppositely charged PNIPAAM on halloysite surfaces: a route to thermo-responsive nanocarriers.
2018
Halloysite nanotubes were functionalized with stimuli-responsive macromolecules to generate smart nanohybrids. Poly(N-isopropylacrylamide)-co-methacrylic acid (PNIPAAM-co-MA) was selectively adsorbed into halloysite lumen by exploiting electrostatic interactions. Amine-terminated PNIPAAM polymer was also investigated that selectively interacts with the outer surface of the nanotubes. The adsorption site has a profound effect on the thermodynamic behavior and therefore temperature responsive features of the hybrid material. The drug release kinetics was investigated by using diclofenac as a non-steroidal anti-inflammatory drug model. The release kinetics depends on the nanoarchitecture of th…