http://chineseinput.net/에서 pinyin(병음)방식으로 중국어를 변환할 수 있습니다.
변환된 중국어를 복사하여 사용하시면 됩니다.
오늘 본 자료
Morphology and elasticity of polystyrene-block-polyisoprene diblock copolymers in the melt
Haenelt, Taida Gil,Georgopanos, Prokopios,Abetz, Clarissa,Rangou, Sofia,Alisch, Doreen,Meyer, Andreas,Handge, Ulrich A.,Abetz, Volker 한국유변학회 2014 Korea-Australia rheology journal Vol.26 No.3
The influence of morphology on the viscoelastic properties of melts of microphase-separated polystyrene-block-polyisoprene (PS-b-PI) diblock copolymers was investigated in oscillatory shear and creep recovery experiments. By means of anionic polymerization, three PS-b-PI diblock copolymers with a narrow molecular weight distribution and different types of morphology (spherical, cylindrical and lamellar microstructure) were prepared. Linear viscoelastic shear oscillations and creep recovery experiments in shear were performed in order to determine the elastic and viscous properties of the diblock copolymers in the melt at small and large time scales. Our analysis reveals that melts of diblock copolymers are characterized by a pronounced elastic behavior leading to a relatively large recoverable deformation in creep recovery experiments. The elasticity of the diblock copolymers is also revealed by the appearance of the creep-ringing effect. Morphological investigations were carried out to establish relations between microstructure and melt elasticity. Since ordering phenomena take place in melts of diblock copolymers until an equilibrium morphology is achieved, the storage modulus G' of diblock copolymer melts increases with time up to a steady-state value.
Morphology and elasticity of polystyrene-block-polyisoprene diblock copolymers in the melt
Taida Gil Haenelt,Prokopios Georgopanos,Clarissa Abetz,Sofia Rangou,Doreen Alisch,Andreas Meyer,Ulrich A. Handge,Volker Abetz 한국유변학회 2014 Korea-Australia rheology journal Vol.26 No.3
The influence of morphology on the viscoelastic properties of melts of microphase-separated polystyreneblock-polyisoprene (PS-b-PI) diblock copolymers was investigated in oscillatory shear and creep recoveryexperiments. By means of anionic polymerization, three PS-b-PI diblock copolymers with a narrow molecularweight distribution and different types of morphology (spherical, cylindrical and lamellar microstructure)were prepared. Linear viscoelastic shear oscillations and creep recovery experiments in shearwere performed in order to determine the elastic and viscous properties of the diblock copolymers in themelt at small and large time scales. Our analysis reveals that melts of diblock copolymers are characterizedby a pronounced elastic behavior leading to a relatively large recoverable deformation in creep recoveryexperiments. The elasticity of the diblock copolymers is also revealed by the appearance of the creep-ringingeffect. Morphological investigations were carried out to establish relations between microstructure andmelt elasticity. Since ordering phenomena take place in melts of diblock copolymers until an equilibriummorphology is achieved, the storage modulus G' of diblock copolymer melts increases with time up to asteady-state value.
Ungar, Goran,Tschierske, Carsten,Abetz, Volker,Holyst, Robert,Bates, Martin A.,Liu, Feng,Prehm, Marko,Kieffer, Robert,Zeng, Xiangbing,Walker, Martin,Glettner, Benjamin,Zywocinski, Andrzej WILEY‐VCH Verlag 2011 Advanced functional materials Vol.21 No.7
<P><B>Abstract</B></P><P>The diversity of phase morphologies observed recently in star‐branched liquid‐crystalline and polymeric compounds containing at least three immiscible segments is reviewed. Bolaamphiphiles and facial amphiphiles with rodlike aromatic cores, two end‐groups, and one (T‐shape) or two (X‐shape) chains attached laterally to the core, form numerous honeycomblike liquid‐crystal phases, as well as a variety of novel lamellar and 3D‐ordered mesophases. Molecular self‐organization is described in bulk phases and in thin films on solid and liquid surfaces, as well as in Langmuir–Blodgett films. The remarkably reversible formation of mono‐ and trilayer films is highlighted. In the bulk, T‐shaped “rod–coil” molecules without appended end‐groups form predominantly lamellar phases if the core is a straight rod, but the bent‐core variety forms hexagonal honeycombs. Furthermore, self‐assembly of “Janus”‐type molecules, is discussed. Also covered is the diversity of morphologies observed in miktoarm star terpolymers, i.e., polymers with three different and incompatible arms of well defined lengths. Similarities and differences are highlighted between the liquid‐crystal morphologies on the 3–15 nm scale and the polymer morphologies on the scale of 10–100 nm. A separate section is dedicated to computer simulations of such systems, particularly those using dissipative particle and molecular dynamics. Of special interest are the recently synthesised X‐shaped tetraphilic molecules, where two different and incompatible side‐chains are attached at opposite sides of the rodlike core. The tendency for their phase separation produces liquid‐crystal honeycombs with cells of different compositions that can be represented as a plane paved with different colored tiles. The independent variation of chain length and “color” creates the potential for developing a considerable range of complex new 2D and 3D soft nanostructures. Analogous X‐shaped rod–coil compounds with unequal side groups are also of considerable interest, forming tubular lyotropic structures capable of confining strings of guest molecules.</P>