Polymer blend

About: Polymer blend is a research topic. Over the lifetime, 18474 publications have been published within this topic receiving 437183 citations. The topic is also known as: polymer mixture & Polymerblend 或者 Polyblend.

Thin film polymer blends undergoing phase separation and wetting: Identification of early, intermediate, and late stages

Abstract: Using forward recoil spectrometry and atomic force microscopy, the phase evolution of a critical blend thin film of deuterated poly(methyl methacrylate) (dPMMA) and poly(styrene-ran-acrylonitrile) (SAN) is found to develop by three distinct stages. During the early stage, dPMMA-rich wetting layers rapidly grow at the air/polymer and polymer/substrate interfaces. A hydrodynamic flow mechanism is proposed based on the scaling of the layer thickness with time, t−1, and the direct observation of an interconnected, bicontinuous morphology across the depletion zone. The lateral wave number of this morphology grows rapidly as t−1 but slows down to t−1/3 when the phase size approaches the film thickness. During the intermediate stage, the wetting layer thins and, concurrently, dPMMA-rich domains spanning the SAN-rich middle grow as t−0.41 in good agreement with an interfacially driven growth model. During the late stage, these capillary fluctuations eventually cause spontaneous rupturing of the middle layer resul...

Excitation of Surface Deformation Modes of a Phase Separating Polymer Blend on a Patterned Substrate

Abstract: The phase separation kinetics of ultrathin deuterated poly(styrene)/poly(butadiene) polymer blend films spun cast onto striped self-assembled monolayer (SAM) substrates is studied by atomic force microscopy (AFM). Fourier transform analysis of the AFM topographic data at various stages of the film pattern development reveals the presence of quantized surface deformation modes. These modes are excited by the phase separation process when the scale of phase separation becomes commensurate with the period of the striped surface pattern. Thus, higher frequency modes become excited at early stages of phase separation, and these excitations decay with time as the phase separation pattern further coarsens. The film ultimately self-organizes into a periodic structure in which the fundamental mode has the largest amplitude. The influence of film thickness on the film morphology in this late stage is also investigated. A decrease in the film thickness leads to surface patterns that match those of the SAM substrates...

High-melting polyolefin copolymer elastomers, catalysts and methods of synthesis

Abstract: This invention relates to high melting polyolefin copolymers suitable as thermoplastic elastomers and catalysts and methods for their synthesis. These elastomeric olefin copolymers are characterized by a mole fraction of crystallizable component XC from about 30 to about 99 %; low glass transition temperatures, below -20 °C, and typically below -50 °C; melting points above about 90 °C; high molecular weights; a molecular weight distribution MW/Mn∫/=10; and a narrow composition distribution between chains of ∫/=15 %. The novel copolymers of the invention range from reactor blends to multiblock copolymers that can be sequentially fractionated into fractions of differing crystallinities, which fractions nevertheless show compositions of comonomers which differ by less than 15 % from the parent polymer (reactor product). The invention also relates to a process for producing such copolymers by utilizing an unbridged, substituted or unsubstituted cyclopentadienyl metallocene catalyst that is capable of interconverting between states with different copolymerization characteristics, which interconversion is controlled by selecting the substituents of the cyclopentadienyl ligands so that the rate of interconversion of the two states is within several orders of magnitude of the rate of formation of a single polymer chain. Where ri > rf the polymer can be characterized as multiblock; where ri < rf, the result is a polymer blend and where ri/rf is close to 1, the resulting polymer is a mixture of blend and multiblock. The metallocene catalysts of the invention are able to interconvert between more than two states, with embodiments of four states being shown in Figure 2.