摘要:

When a physical chemist looks at living matter, he sees watery bits and fatty or lipid bits and, in spite of the old saying that oil and water don't mix, there seems to be a lot of mixing and peculiar mixing at that; both lipids in water and water in lipids. Nor is this so strange because the model of lipid phase and water phase lying in contact without any interaction would seem to be a singularly useless one for the complex co-ordinated activities which we call life. Nevertheless the triglycerides are such inert lipids, which is a useful property as depot fats,1but one which requires pancreatic lipolysis for intestinal absorption; that is, conversion to lipids which do interact with water and aqueous bile salt solutions.

ISSN:0369-1152    

DOI:10.1080/15421406908084864

出版商:Taylor & Francis Group    

年代:1969

数据来源: Taylor

摘要:

Some models for the molecular structures of liquid crystals including a ferroelectric liquid are discussed. It is shown that a smectic liquid with a layered structure, in which the preferred orientation of the molecular axis is inclined against the layers, has some similarities with a nematic liquid. Such a tilted smectic liquid may also have a twisted modification corresponding to a twisted nematic or cholesteric liquid crystal. Attention is drawn to an optically isotropic texture of a cholesteric liquid. A proposal is made for its molecular structure in which a fairly regular, lattice-like arrangement of alignment singularities is assumed. Twist waves in nematic liquids are regarded and numerical estimations are made for their wave velocity and damping inp-azoxyanisole. It is concluded that the damping is too strong for an observation of such waves.

ISSN:0369-1152    

DOI:10.1080/15421406908084865

出版商:Taylor & Francis Group    

年代:1969

数据来源: Taylor

摘要:

Insofar as liquid crystals can exist in lifeless organic substances as well as in living systems, we have to differentiate for the purpose of this lecture between inanimate and animate matter; in other words, we have to ask what, insofar as the liquid crystalline state is involved, is the unique feature of living matter or protoplasm. This question is ultimately part of a much greater riddle but our immediate problem is to see whether the liquid crystalline state is an integral or merely an incidental feature of cellular and extracellular substance in living organisms.

ISSN:0369-1152    

DOI:10.1080/15421406908084866

出版商:Taylor & Francis Group    

年代:1969

数据来源: Taylor

摘要:

We have studied the structure of liquid crystalline phases ofA-Bblock copolymers by small-angle X-ray scattering. We have found three types of structure: lamellar, hexagonal and cubic. We have also shown the influence on the structural type and structural parameters of the following factors: concentration and nature of the solvent, molecular weight and composition of the copolymer.

ISSN:0369-1152    

DOI:10.1080/15421406908084867

出版商:Taylor & Francis Group    

年代:1969

数据来源: Taylor

摘要:

Although publications concerning advances in synthesis and the role of molecular geometry in liquid crystallinity have not been numerous since the last conference in 1965, I have nevertheless had to be somewhat selective in the material which I have chosen to review in the available time. Broadly speaking, I have selected those areas of study which have given rise to new results which can be logically related to past experience in the field of molecular structure and the properties of liquid crystals. To this end, I have divided the lecture into three parts, of which the first is largely introductory.

ISSN:0369-1152    

DOI:10.1080/15421406908084868

出版商:Taylor & Francis Group    

年代:1969

数据来源: Taylor

摘要:

We describe continuum theory now being used to describe macroscopic behavior of liquid crystals of nematic type. Two types of predictions are discussed. The first concerns the propagation of orientation waves. The second area is viseometry, including effects of simple electromagnetic fields. We discuss some unusual size effects predicted when such fields are absent.

ISSN:0369-1152    

DOI:10.1080/15421406908084869

出版商:Taylor & Francis Group    

年代:1969

数据来源: Taylor

摘要:

The science of liquid crystals is a part of general crystallography, which is the physical chemistry of crystals and related objects. Nowadays it is generally accepted that the so-called “liquid crystals” are neither real crystals nor real liquids. Whereas the misunderstandings produced by the name “liquid crystals” may be considered as overcome, this name has become accepted as historically established, indicating the referred matter to all who may be interested. In future denominations closer to the real nature of these objects may become more popular. The name “mesomorphic states” is already widespread. There is no doubt about the accurate meaning of “meso”, the intermediate position between amorphous and crystalline, but “morphic” and “state” mostly indicate the relation to the structure only, the relation to the space coordinates, whereas in physics, physical chemistry and generalized crystallography we have to deal with the time coordinate as well, with processes such as dissolution and growth, with equilibrium and temperature. So, the relation to thermodynamics would be still better expressed by the word “mesophases”, since the definition of “phase” is: a homogeneous system in thermic equilibrium. It is symmetric in relation to time. Of these so-called “liquid crystals” only two types of phase structure are well known: the nematic and the smectic. In the real crystals the coordinate transfer from one molecule to the next is characterised by the periodicity of all three translations and all three rotations in space. In the smectic state only one translation period and two rotational periods exist. And in the nematic state only the two rotational periods remain. In other words, the smectic phases show a layered structure, and the nematic phases a fibrous one. Some authors1maintain that certain substances exhibit a higher number of different phases. Principally it is not excluded that one substance may present more than one smectic or more than one nematic phase. For example in one smectic phase the translation period may be twice that in the other.

ISSN:0369-1152    

DOI:10.1080/15421406908084870

出版商:Taylor & Francis Group    

年代:1969

数据来源: Taylor

摘要:

“Phases of higher order” or “superphases” are homogeneous systems in thermodynamic equilibrium as are ordinary phases. They are distinguished by the size of their structural elements and by the nature of the forces determining the equilibrium. The size is that of colloidal particles, that is of 10–5up to 10–7cm; the equilibrium is determined by electric forces arising from surface charges and ionic double layers. This indicates that the immersion medium is mainly water, which is able to produce high surface charges and notably thick double layers on account of its exceptionally high dielectric constant.

ISSN:0369-1152    

DOI:10.1080/15421406908084871

出版商:Taylor & Francis Group    

年代:1969

数据来源: Taylor

摘要:

Since the discovery by Saupe and Englert that a nematic phase is a satisfactory solvent for high resolution nuclear magnetic resonance (NMR) studies, the variety of liquid crystal phases which have been found useful in NMR experiments has greatly increased. The resonance studies have increased our understanding of the structure of the solvent mesophases, and of their interactions with solute molecules.

ISSN:0369-1152    

DOI:10.1080/15421406908084872

出版商:Taylor & Francis Group    

年代:1969

数据来源: Taylor

摘要:

A lyotropic liquid crystalline phase has been used as an orienting matrix for NMR studies. The solvent and orientation properties of this phase are somewhat different from those of thermotropic nematogens. Spinning samples can be used facilitating the recording of well-resolved spectra suitable for analysis. The spectrum of ethanol has been recorded and analyzed in full by an iterative computer procedure. It is shown that the preferred orientation of ethanol in the mesophase is such that the C—C—O plane is perpendicular to the magnetic field.

ISSN:0369-1152    

DOI:10.1080/15421406908084873

出版商:Taylor & Francis Group    

年代:1969

数据来源: Taylor