173 research outputs found
Process for preparing zinc dicarboxylate and use thereof as a catalyst in the synthesis of polyalkylene carbonate from co2 by heterogeneous catalysis
The present invention relates to a process for the synthesis of a zinc-based compound having general formula (I): wherein L is selected in the group consisting of: NO3, CH3CO2, (SO4)0.5, halide, and acetyl acetonate (AcAc), 2x = y + z; wherein x is comprised between 1 and 5, y is comprised between 1 and 8, z is comprised between 1 and 2, and n is comprised between 0 and 20. Said zinc-based compound is then used for the synthesis of a zinc dicarboxylate catalyst to be used for the heterogeneous catalytic copolymerization of a polyalkylene carbonate starting from CO2 and an alkyl epoxide, preferably containing at least 3 atoms of carbon, said polyalkylene carbonate being characterised by chemical-physical and mechanical properties which make it advantageous for a variety of different applications
Process for preparing zinc dicarboxylate and use thereof as a catalyst in the synthesis of polyalkylene carbonate from co2 by heterogeneous catalysis
Polyalkylene carbonate obtained from biodegradable co2 and with self-healing properties
The present invention relates to a polyalkylene carbonate, preferably PRC, and the use thereof in packaging, in coating surfaces, in cosmetics, in the biomedical or textile sector or to produce composite materials or moisture absorption devices. Preferably, said polyalkylene carbonate is obtained by reacting CO2 with an alkyl epoxide preferably containing at least 3 atoms of carbon, preferably propylene oxide, in the presence of a zinc dicarboxylate catalyst; said catalyst being obtained by reacting, with a preferably saturated aliphatic dicarboxylic acid, a zinc-based compound comprising a mixture of ZnO and a compound having the general formula (I): Znx(0H)y(L)z-nH2 O (I) wherein L is selected in the group consisting of: NO3, CH3CO2, (SO4)0.5, halide, and acetyl acetonate (AcAc), 2x = y + z; wherein x is comprised between 1 and 5, y is comprised between 1 and 8, z is comprised between 1 and 2, and n is comprised between 0 and 20
Phenomenological modeling of the stress-free two-way shape-memory effect in semi-crystalline networks: Formulation, numerical simulation, and experimental validation
Polymers exhibiting the stress-free two-way shape-memory effect (SME) represent an appealing solution to
achieve self-standing reversible actuation that is a fundamental feature required by numerous applications. The
present paper proposes a one-dimensional continuum phenomenological framework to model single-component
semi-crystalline polymer networks exhibiting both the one-way SME and the two-way SME under stress and
stress-free conditions. A comprehensive experimental campaign is first performed on semi-crystalline networks
based on poly(ε-caprolactone) (PCL) to characterize the mechanical and thermal properties as well as the
one-way and two-way shape memory behavior of the material under different thermo-mechanical conditions.
The results guide the formulation of the model, elucidating the selection of the control and phase variables and
motivating the choice of their evolution laws. Model capabilities are then demonstrated against experimental
data. All the phenomena that influence the stress-free two-way SME, including the actuation temperature,
heating/cooling rates, applied stress/strain, and the amount of skeleton and actuation phase, are analyzed and
discussed, giving new important insight for application developme
Master curves for the mechanical reinforcement of diene elastomers with sp2 carbon allotropes
sp2 carbon allotropes are efficient reinforcing fillers for polymer melt and
elastomers: carbon black (CB) has been used since early 1900’s and nanofillers such
as carbon nanotubes (CNT), graphene and graphene related materials (GRM) have
increased their importance over the last decades. Nanofillers can definitely
establish larger interfacial area with the polymer matrix than CB and great impact
on material properties is thus expected. However, it is widely acknowledged that
they will not be able to completely replace CB. Hence, increasing research efforts
are on hybrid systems based on CB-CNT and CB-GRM [1]. Research objective is to
identify common features and behaviour of nano (CNT, GRM) and nanostructured
(CB) sp2 carbon allotropes.
In this work, initial modulus was determined by means of dynamic-mechanical
shear measurements of composites based on either poly(1,4-cis-isoprene) or
poly(styrene-co-butadiene) as the rubber and either CB or CNT or GRM or hybrid
systems as the reinforcing fillers.
Filler-polymer interfacial area (i.a.), calculated as the product of filler surface
area, density and volume fraction, was used to establish a common correlation
with the composite initial modulus. A sort of master curve was derived, able to fit
all the points up to interfacial area of about 27 μm-1, corresponding to remarkable
filler content.
Much better efficiency was shown by carbon fillers, when composites were
prepared through latex blending. To allow easy dispersion in rubber latex, sp2
carbon allotropes were functionalized with a serinol derivative: 2-(2,5-dimethyl-
1H-pyrrol-1-yl)-1,3-propanediol (serinol pyrrole, SP) [2, 3], shown in Figure 1
Curcumin and Novel Synthetic Analogs in Cell-Based Studies of Alzheimer’s Disease
Alzheimer’s disease (AD) is a chronic neurodegenerative disorder that is associated with the most common type of dementia and is characterized by the presence of deposits of the protein fragment amyloid beta (Aβ) in the brain. The natural product mixture of curcuminoids that improves certain defects in innate immune cells of AD patients may selectively enhance Aβ phagocytosis by alteration of gene transcription. In this work, we evaluated the protective effects of curcuminoids in cells from AD patients by investigating the effect on NF-κB and BACE1 signaling pathways. These results were compared to the gene expression profile of the clearance of Aβ. The minor curcumin constituent, bisdemethoxycurcumin (BDC) showed the most potent protective action to decrease levels of NF-κB and BACE1, decrease the inflammatory cascade and diminish Aβ aggregates in cells from AD patients. Moreover, mannosyl-glycoprotein 4-beta-N-acetylglucosaminyltransferase (MGAT3) and vitamin D receptor (VDR) gene mRNAs were up-regulated in peripheral blood mononuclear cells from AD patients treated with BDC. BDC treatment impacts both gene expression including Mannosyl (Beta-1,4-)-Glycoprotein Beta-1,4-N-Acetylglucosaminyltransferase, Vitamin D and Toll like receptor mRNA and Aβ phagocytosis. The observation of down-regulation of BACE1 and NF-κB following administration of BDC to cells from AD patients as a model system may have utility in the treatment of asymptomatic AD patients
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