Search results for "Polymers"
showing 10 items of 3567 documents
Titanium (IV) chloride complexes with salen ligands supported on magnesium carrier: Synthesis and use in ethylene polymerization
2009
The magnesium support with the formula MgCl 2 (THF) 0.32 (Et 2 AlCl) 0.36 was used for immobilization of salen complexes of titanium [Ti(salen)Cl 2 , Ti(salen(O-Me) 2 )Cl 2 ]. The effects of the catalyst composition (i.e. type of titanium complex and type of activator), polymerization temperature, polymerization time, and the effect of comonomer (1-octene) on the activity of the obtained supported catalysts, on the polymer characteristics (molecular weight, molecular weight distribution, melting point), and on the polymer morphology were studied. The findings were compared to those obtained for corresponding unsupported systems. Catalysts immobilization results in considerable changes in ca…
Preparation of Polymeric Nanoparticles by Photo-Crosslinking of an Acryloylated Polyaspartamide in w/o Microemulsion
2004
Biodegradable polymeric nanoparticles have been prepared by UV irradiation of an acryloylated water soluble polymer by an inverse microemulsion. The starting polymer was a α,β‐poly(N‐2‐hydroxyethyl)‐D,L‐aspartamide (PHEA) partially functionalized with glycidyl methacrylate (GMA) in order to introduce reactive vinyl groups in the side chain. The PHEA‐GMA copolymer obtained (PHG) was crosslinked by UV irradiation of the inverse microemulsion prepared by mixing an aqueous solution of PHG with propylene carbonate (PC)/ethyl acetate (EtOAc) in the presence of sorbitan trioleate (SPAN 85) as surfactant. Nanoparticles obtained were characterized by FTIR spectrophotometry, transmission electron mic…
Halloysite Nanotubes Coated by Chitosan for the Controlled Release of Khellin
2020
In this work, we have developed a novel strategy to prepare hybrid nanostructures with controlled release properties towards khellin by exploiting the electrostatic interactions between chitosan and halloysite nanotubes (HNT). Firstly, khellin was loaded into the HNT lumen by the vacuum-assisted procedure. The drug confinement within the halloysite cavity has been proved by water contact angle experiments on the HNT/khellin tablets. Therefore, the loaded nanotubes were coated with chitosan as a consequence of the attractions between the cationic biopolymer and the halloysite outer surface, which is negatively charged in a wide pH range. The effect of the ionic strength of the aqueous medium…
Vanadium catalysts for ethylene-norbornene copolymerization
2020
Kopolimery cyklicznych olefin (COCs) stanowią obiecującą grupę materiałów o specyficznych, możliwych do zaprojektowania właściwościach. Szczególnym zainteresowaniem w tej grupie związków cieszą się kopolimery etylenu z norbornenem. Do ich syntezy stosuje się różnorodne kompleksy metali przejściowych, przede wszystkim pierwiastków z grupy 4. Artykuł stanowi przegląd literatury dotyczącej wykorzystania katalizatorów wanadowych z różnego rodzaju ligandami w syntezie kopolimerów etylenu z norbornenem. Opisano wpływ ligandów i warunków prowadzenia reakcji na aktywność oraz wybrane właściwości otrzymanych kopolimerów.
Studies of ethylene/1-hexene copolymerization over zirconocene catalyst supported on MAO-modified MgCl2(THF)2. The effect of copolymerization conditi…
2003
Composition of catalytic system and copolymerization reaction conditions influence on heterogeneity of ethylene/1-hexene copolymers obtained over MgCI2(THF)2/MAO/Cp2ZrCl2/MAO catalyst was studied. One of the DSC techniques, i.e. successive self-nucleation/annealing (SSA) method allowing separation of the polymer into fractions with differing chemical composition in result of alternating crystallization and melting cycles was applied. It was found that the intermolecular heterogeneity exists inside all studied samples irrespective of the reaction conditions (temperature and time) and the catalyst composition (Al/Zr molar ratio). It was also confirmed that catalyst composition has a considera…
The Form is Not a Proper Part in Aristotle’s Metaphysics Z.17, 1041b11–33
2018
When Aristotle argues at the 'Metaphysics' Z.17, 1041b11–33 that a whole, which is not a heap, contains ‘something else’, i.e. the form, besides the elements, it is not clear whether or not the form is a proper part of the whole. I defend the claim that the form is not a proper part within the context of the relevant passage, since the whole is divided into elements, not into elements and the form. Different divisions determine different senses of ‘part’, and thus the form is not a part in the same sense as the elements are parts. I object to Koslicki’s (2006) interpretation, according to which the form is a proper part along the elements in a single sense of ‘part’, although she insists th…
Flow Behavior of Chain and Star Polymers and Their Mixtures
2018
Star-shaped polymers show a continuous change of properties from flexible linear chains to soft colloids, as the number of arms is increased. To investigate the effect of macromolecular architecture on the flow properties, we employ computer simulations of single chain and star polymers as well as of their mixtures under Poiseuille flow. Hydrodynamic interactions are incorporated through the multi-particle collision dynamics (MPCD) technique, while a bead-spring model is used to describe the polymers. For the ultradilute systems at rest, the polymers are distributed uniformly in the slit channel, with a weak dependence on their number of arms. Once flow is applied, however, we find that the…
Mastering the Tools: Natural versus Artificial Vesicles in Nanomedicine
2020
Naturally occurring extracellular vesicles and artificially made vesicles represent important tools in nanomedicine for the efficient delivery of biomolecules and drugs. Since its first appearance in the literature 50 years ago, the research on vesicles is progressing at a fast pace, with the main goal of developing carriers able to protect cargoes from degradation, as well as to deliver them in a time- and space-controlled fashion. While natural occurring vesicles have the advantage of being fully compatible with their host, artificial vesicles can be easily synthetized and functionalized according to the target to reach. Research is striving to merge the advantages of natural and artifici…
Systematic Study of a Library of PDMAEMA-Based, Superparamagnetic Nano-Stars for the Transfection of CHO-K1 Cells.
2017
The introduction of the DNA into mammalian cells remains a challenge in gene delivery, particularly in vivo. Viral vectors are unmatched in their efficiency for gene delivery, but may trigger immune responses and cause severe side-reactions. Non-viral vectors are much less efficient. Recently, our group has suggested that a star-shaped structure improves and even transforms the gene delivery capability of synthetic polycations. In this contribution, this effect was systematically studied using a library of highly homogeneous, paramagnetic nano-star polycations with varied arm lengths and grafting densities. Gene delivery was conducted in CHO-K1 cells, using a plasmid encoding a green fluore…
A Biodegradable, Bio-Based Polymer for the Production of Tools for Aquaculture: Processing, Properties and Biodegradation in Sea Water
2023
Bio-based, biodegradable polymers can dramatically reduce the carbon dioxide released into the environment by substituting fossil-derived polymers in some applications. In this work, prototypes of trays for aquaculture applications were produced via injection molding by using a biodegradable polymer, Mater-Bi®. A characterization carried out via calorimetric, rheological and mechanical tests revealed that the polymer employed shows properties suitable for the production of tools to be used in aquaculture applications. Moreover, the samples were subjected to a biodegradation test in conditions that simulate the marine environment. The as-treated samples were characterized from gravimetrical,…