Search results for "MACRO"

Structure of bottle-brush brushes under good solvent conditions: a molecular dynamics study.

2011

We report a simulation study for bottle-brush polymers grafted on a rigid backbone. Using a standard coarse-grained bead-spring model extensive molecular dynamics simulations for such macromolecules under good solvent conditions are performed. We consider a broad range of parameters and present numerical results for the monomer density profile, density of the untethered ends of the grafted flexible backbones and the correlation function describing the range that neighboring grafted bottle-brushes are affected by the presence of the others due to the excluded volume interactions. The end beads of the flexible backbones of the grafted bottle-brushes do not access the region close to the rigid…

Chitin: A Structural Biopolysaccharide

2009

Chitin is a naturally occurring fibre-forming polymer that plays a protective role in many lower eukaryotes similar to that of cellulose in plants. Chemically it is a long-chain unbranched polysaccharide made of N-acetylglucosamine residues; it is the second most abundant organic compound in nature, after cellulose. Taking into account the structural role played by chitin, its metabolism (synthesis and degradation) is essential for different morphogenetic events. Absent in vertebrates and plants, chitin represents a parasite-specific target for chemotherapeutic attack and also plays a role in host immune responses. Because of its abundance in nature and its properties, biotechnological appl…

1977

Polymer Structure Characterization-From Nano to Macro Organization. By Richard A. Pethrick.

2008

Nonlinear Macromolecules by Ring-Opening Polymerization

2012

Ring-opening polymerization (ROP) is a well-established method for the controlled synthesis of linear polymers, which can be found in various everyday applications. However, during the past decades, there has been an increasing interest in the generation of nonlinear highly branched polymers, profiting from the fascination created by the structurally perfect dendrimers. The applicability of various heterocyclic monomers renders the ring-opening multibranching polymerization (ROMBP), a versatile tool for the generation of multifunctional hyperbranched polymers. First, the historical key steps leading to the development of ROMBP are described, which is the basis for the controlled synthesis o…

Thermo- and light responsive micellation of azobenzene containing block copolymers

2010

In this communication, the synthesis and characterization of thermo- and light responsive block copolymers is reported. PEO-b-PNIPAM polymers with azobenzene moieties were prepared and analyzed by turbidimetry, fluorescence, NMR and DLS measurements. A temperature controlled reversible formation as well as a light induced disruption and reformation of micellar structures in water was found.

MCM-41 and related materials as media for controlled polymerization processes

1994

The synthesis of mesoporous MCM-41 type materials based on transition metal oxides and the polymerization of several monomers within MCM-41 is presented with the aim to specifically investigate the effects of the interface and confinement on host-guest interactions. In addition to standard MCM-41, material based on transition metal oxides is obtained although template removal has been unsuccessful for such compounds until now. In situ polymerization of styrene, methyl methacrylate and vinyl acetate is possible within the mesopore system. The properties of some of the encapsulated polymers differ markedly with those obtained in the bulk.

Emergence, evidence, and effect of junction clustering in supramolecular polymer materials

2021

A significant fraction of biomaterials consists of supramolecular polymers and networks formed by non-covalent interactions between associative motifs. They typically contain complex structures in which on top of binary associations, phase-separation and aggregation of associative junctions occur. Such hierarchical assemblies have significant influences on the dynamics as well as the physical and mechanical properties of the materials. Similar to supramolecular biomaterials, aggregation of associative junctions has also been frequently reported to occur in synthetic supramolecular polymers and networks. Engineering of such secondary structures in a sense to create and control the extent of …

Effects of UVB radiation exposure from the molecular to the organism level in macrophytes from shallow Mediterranean habitats

2015

Abstract The available data on the effects of UVB radiation (UVBR) are scarce for submerged macrophytes, particularly charophytes. We studied the effects of UVBR on Chara baltica, Chara hispida, Chara vulgaris, Nitella hyalina and Myriophyllum spicatum, collected from shallow Mediterranean waterbodies. In a short-term laboratory experiment, we subjected these species to three different UVBR treatments corresponding to daily biologically effective integrated doses of 0, 1 and 6 kJ m−2. The analysed response variables were DNA damage, UV-absorbing compounds (both the methanol-soluble–SUVACs- and, for the first time in charophytes, the methanol-insoluble cell wall-bound fraction–WUVACs-), the …

Mesoscopic gel at low agarose concentration in water: a dynamic light scattering study

1995

Previous work in our laboratory has shown that at very low agarose concentration in water gelation still occurs within mutually disconnected, high concentration regions generated by spinodal demixing. The freely diffusing particles obtained in these conditions are studied in the present work by depolarized dynamic light scattering and probe diffusion experiments. These particles are found to behave as large (in fact, mesoscopic) polymer fibers entangled in a continuously rearranged mesh with scaling parameters typical of partially flexible, neutral chains. The present results allow specifying the notion of mesoscopic gelation. They also reveal that the same symmetry-breaking mechanism that …