Semiflexible LCP

Isothermal Crystallization Kinetics of Compatibilized Blends of Polyolefins with a Semiflexible LCP... 

The investigation of the compatibilization and crystallization of blends of polyolefins with a semiflexible LCP leads to the following conclusions the compatibilization of polyolefin/LCP blends has been realized successfully by the addition of ad hoc synthesized polyolefin-g-LCP copolymers. The compatibilization results into materials, characterized by a stabilized morphology, improved crystallization kinetics under nonisothermal and isothermal conditions, and enhanced mechanical properties. Moreover, polyolefin processability has been enhanced by the addition of LCP, even in the presence of compatibilizers. New high quality materials with improved processability have been produced by technologies, which are economic, friendly to the environment, and socially acceptable. 

An other important concept for the modification of LCPs is the incorporation of flexible spacers between mesogenic units. These semiflexible LCPs have been extensively investigated and have to be distinguished from the above systems. As a consequence, a separate contribution in this handbook is devoted to this class of LCPs (Sect. 2 of this Chapter). 

Addition of a semiflexible LCP to LLDPE decreased melt viscosity and nucleated crystallization. This increased modulus of the LLDPE [198]. 

Transmission electron microscopy (TEM) studies conducted by Thomas et al. [62,63] have permitted direct visualization of the molecular director distribution in flow-oriented thin films prepared from semiflex-ible thermotropic LCPs of the following structure ... 

For the purpose of discussing mesophase formation in polymers it is conveiuent to partition the polymers into two categories and introduce abbreviations that refer to these categories. Polymerized liquid crystals, here abbreviated PLCs, are derived from known, low molecular weight monomer liquid crystals (MLCs) that contain polymerizable functionality (e.g. vinyl units). We designate liquid-crystalline polymers (LCPs) to be semiflexible, linear polymers that are structurally related to conventional engineering thermoplastics, i.e. polymers derived from poly(ester)s, poly(amide)s, poly(imide)s, etc. We will examine the attributes of polymerized liquid crystals first, stressing the similarities between their properties and those of MLCs. 

The general predictions of Eq. (5.14) are in agreement with experiment for a variety of lyotropic LCPs [88]. One consequence of this theory for a system of polydisperse rods (a distribution of x values) is the possibility of fractionation [89] longer rods would distribute themselves into the anisotropic LC phase while short ones would be relegated to the isotropic phase in the two-phase regime. The theory can also be extended [90] to make predictions about ternary mixtures - rods, random coUs, and solvent - and is in agreement with experimental observations [91] that indicate the strong incompatibility of the two kinds of polymers. It has been adapted to treat semiflexible polymers also. 

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