Search results for "plate"

Cylindrical polymer brushes – Anisotropic building blocks, unimolecular templates and particulate nanocarriers

2016

Abstract This article presents an overview of the latest key developments and research activities in the area of cylindrical polymer brushes (CPBs), also known as ‘molecular bottlebrushes’. CPBs consist of a polymer backbone containing polymer side chains that cause the backbone to extend and adopt a worm-like conformation. The extent of backbone stretching and the aspect ratio of CPBs is determined by the length and grafting density of the side chains. The latest developments in controlled/living polymerisation techniques led to novel and more efficient ways of producing delicate polymer architectures, such as block copolymer CPBs, and resulted in a considerable expansion of the field of a…

Complete in-plane elastic characterisation under tensile tests of angle-ply laminates composed of polymer-matrix layers

2002

In this paper we present a new strategy to completely characterise the in-plane elastic properties of a large range of angle-ply laminates using only unidirectional tests. We consider laminates having the same number of identical plies in the α and – α directions. This new method uses some preceding results found by Verchery for orthotropic laminates, namely the conditions of existence of a specific direction ω, in which the shear-extension coupling is null. The characterisation of the laminate is then made using the results of three tensile tests: two in the orthotropy axes, and the third one in the ω direction, in order to have always a pure one-dimensional state of stress. We show that …

Origin of the low-frequency plateau and the light-scattering slow mode in semidilute poly(ethylene glycol) solutions

2019

A low-frequency plateau is often found in the rheological spectra of various kinds of semidilute solutions of polymers and other colloids; also, many such solutions have been reported to show slow-modes in their dynamic light scattering autocorrelation functions. Both these observations may lead to the hypothesis of weak associative network structures built by the dissolved polymer chains or colloidal building blocks. To challenge this hypothesis, we conduct a series of comparative studies on semidilute solutions of poly(ethylene glycol) by using classical rheology as well as passive microrheology based on dynamic light scattering, along with structural studies using static light scattering…

Imprinted Polymers with Memory for Small Molecules, Proteins, or Crystals

2000

Effect of the elongational flow on morphology and properties of polypropylene/graphene nanoplatelets nanocomposites

2018

Abstract In this work the effect of the presence of graphene nanoplatelets (GnP) on the morphology and mechanical properties of polypropylene/GnP nanocomposites has been investigated when these polymer systems are subjected to non-isothermal elongational flow in a melt spinning operation. The presence of the GnP magnifies the effect of the elongational flow. Indeed, the elastic modulus and the tensile strength of nanocomposites increases with the orientation more than that observed for the pure matrix. Moreover, the elongation at break increases at low values of the draw ratio for the nanocomposites, while, the matrix shows the expected decrease in deformability. These effects have been cor…

Micropropagation of Metrosideros excelsa

2008

Multiple shoots were induced on stem segments of a 8-year-old plant of Metrosideros excelsa Sol ex Gaertn. ‘Parnel’. Axillary shoots produced on uncontaminated explants were excised, segmented and recultured in the same medium to increase the stock of shoot cultures. The Murashige and Skoog (MS) medium, augmented with different concentrations of 2- isopenthenyladenine (2iP) and indole-3-acetic acid (IAA), either singly or in combinations, as potential medium for shoot multiplication by nodal segments was tested. In the following experiment equal molar concentrations of four cytokinins [2iP, kinetin, zeatin and N6-benzyladenine (BA)] in combination with equal molar concentrations of three au…

ChemInform Abstract: Carbohydrates as Chiral Templates: Asymmetric Ugi-Synthesis of α-Amino Acids Using Galactosylamines as the Chiral Matrices.

1989

ChemInform Abstract: Carbohydrates as Chiral Templates: Diastereoselective Ugi Synthesis of (S)-Amino Acids Using O-Acylated D-Arabinopyranosylamine …

1990

Abstract Enantiomerically pure (S)-amino acids are synthesized via a highly diastereoselective Ugi reaction using 2,3,4-tri-O-pivaloyl-α-D-arabinopyranosylamine as the chiral template.

ChemInform Abstract: Carbohydrates as Chiral Templates in the Stereoselective Synthesis of . beta.-Amino Acids

2010

ChemInform Abstract: Carbohydrates as Chiral Templates: Diastereoselective Synthesis of N- Glycosyl-N-homoallylamines and β-Amino Acids from Imines.

2010

Complexing properties and chirality of carbohydrates were utilized in diastereoselective reactions of 0-pivaloylated N-galactosylimines with allylsilanes and -stannaries. With dyltrimethylsilane in the presence of SnCl4, imines 2 of aromatic and heteroaromatic aldehydes were converted to homdylamines 3, giving ratios of diastereomers higher than 7:1. No addition products derived from α-anomeric aromatic imines were formed. Aliphatic homdylamines 3 were synthesized by using allyltributylstannane in the presence of SnCl4. Both α- and β-anomeric aliphatic imines reacted with the allylstannane. They gave the same ratio of diastereomers and showed the same sense of asymmetric induction.