Charge carrier transport, viscosity, and diffusion in liquid crystals to determine effect of weak electric and magnetic fields on biological system

Kusabayashi, S.

Labes, M. M.

Laronge, T. M.

English

NASA Technical Reports Server

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Mechanisms for  the Effects of Electric and 
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Magnetic Fields on Biological Systems 
S .  Kusabayashi, T. M. Laronge andM. M. Labes 
Semiannual Status Report No. 1 
NASA Grant NGR 39-004-015 
June - Dec. 1967 
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I Drexel Institute of Technology 
Chemistry Department 
Philadelphia, Pennsylvania 19104 
https://ntrs.nasa.gov/search.jsp?R=19680003847 2020-03-12T11:43:28+00:00Z
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Mechanism for  the Effects of Electric and 
Kagnetic Fields on Biological Systems 
Introduction 
Weak electrical  andmagnetic f ie lds  have been reported 
t o  influence a wide variety of biological phenomena. 
effects, for  example, have been attributed t o  magnetic f i e l d  
gradients as small as 
many purported effects on growth rates of animals and plants, 
Biomagnetic 
oersteds, and the l i terature  contains 
gemination of seeds, tumor growth, etc. at  modest magnetic f ie lds  
of the order of 1000 oersteds. 
controversial and have been greeted with a considerable amount of 
These reports, i n  general, are 
skepticism. The absence of explanations a t  a molecular level of 
how a weak magnetic o r  electric f i e ld  can influence molecular 
behaviors has hindered the development of any reasonable under- 
standing o r  approach t o  the controversy. 
I t  is the purpose of th i s  study t o  examine molecular 
level explanations of such phenomena. During the i n i t i a l  period 
we have focused attention on the possibility that  the liquid 
crystalline phase may well be a suitable model f o r  the structure 
of many biological organelles . 
(1) 
1 The principal investigator has 
See for  example, C. Robinson, Trans .  Farad. SOC. - 62, 571 
(1956); G .  T. Stewart, Nature, 183, 873(1959); Intern. Liquid 
Crystal Conf., Kent State Univ., Kent, Ohio, August 15-20, 1965, 
Part ' I ,  Molecular Crystals, 1, 201 (1966). 
- 2 -  
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presented arguments which suggest that the purported effects of 
~ c d e s t  mqpetic fields (lOOO-SOOO oei-ste&j on iiving systems 
may w e l l  be explained on a molecular level by the response of the 
transport properties of liquid crystalline materials to  these 
modest magnetic fields . To examine this  hypothesis, we have 2 
(2) M. M. Labes, Nature, 211, 5052(1966). 
decided to  examine charge transport,viscosity,and diffusion in  
the liquid crystalline phase under the influence of a magnetic 
field.  
Charge Carrier Transport in  Liquid Crystals 
In order to  study charge transport in an organic material, 
I 
it is now clearly established that  the most effective studies 
involve photoconductivity and d r i f t  mobility measurements 3 . Dark 
(3) See 0. H. LeBlanc in "Physics and Chemistry of the Organic 
Solid State", Ed. by D. Fox, M. M. Labes and A. Weissberger, Inter- 
science Division, John Wiley F, Sons, Inc.; New York, 1967. 
conductivity measurements are difficult ,  i f  not impossible, t o  
~ interpret on insulating solids, and it seemed most appropriate to 
attempt to find a liquid crystalline material i n  which a reasonable 
photoconductive gain could be observed. 
probe the transitions from anisotropic solid t o  liquid crystal to  
I t  is then possible t o  
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isotropic liquid by measuring f i r s t l y  steady s ta te  photoconductivity 
and secondly d r i f t  mobility via a l ight  pulse excitation technique. 
- 3 -  
: 
There is no literature on the photoconductive properties 
oI' liquid czystais, and consequently we undertook a screening pro- 
gram in which a representative group of liquid crystals were chosen 
because their structures incorporated aromatic moieties. 
dark and photoconductivity of these materials at room temperature 
(solid phase) was studied. We were pleasantly surprised to find 
many compounds with high photoconductive response. A few compounds 
also appear to undergo some interesting photoreactions in the solid 
The 
phase, and photovoltaic effects were also observed. 
The values of dark and photoconductivity on representative 
liquid crystals are given in Table I. 
results in detail at this time, since it is our intention to do 
detailed work on the system or systems which show the highest 
photoconductive response. 
We will not discuss these 
However, three of these materials appear 
to be very good photoconductors, demonstrating photoconductive 
responses as high as have typically been observed for organic 
materials. These are p-p'-dimethoxystilbene(K), p-anisylidene-p- 
biphenylamine (H) and p- anisylideneaminophenyl acetate (G) . The 
maximum photoresponse observed was a factor of 1000. Diethyl p-p'- 
azoxydicinnamate (D) also shows a large photoresponse, which appears 
to be accompanied by some photochemical dimerization. 
cases, very large photovoltaic effects were observed which must 
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be studied further. 
These measurements were carried out by illuminating 
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sandwich cells made by melting the liquid crystals between two 
conducting glass or  quartz plates. 
electrodes were'used. 
Either t i n  oxide or  gold 
Conductivity was measured with a Cary 401 
Vibrating Reed Electrometer. 
150 watt xenon lamp whose beam w a s  passed through a water f i l t e r .  
The l ight  source was  ~ 2 5  cm to ta l  distance from the sample. 
applied voltage (from a Keithley Model 241 power supply) w a s  
negative on the illuminated side of the sample. 
Illumination was supplied by a 
The 
Viscosity of and Diffusion i n  Liquid Crystals 
In order to judge the effect  of amagnetic f ie ld  on 
mass transport i n  liquid crystals, we have decided t o  perform 
viscosity and diffusion measurements. 
that diffusion rates i n  nematic liquid crystalline materials 
can be influenced by modest magnetic f ie lds  (1000 to  5000 oersteds). 
The l i terature  indicates 
4 Svedberg in  the early 1900's reported diffusion rates i n  a mixed 
liquid crystal system of p-azoxyanisole and p-azoxyphenetole and 
finds a 40% difference in  rates of impurity diffusion when a 3500 
oersted magnetic f i e ld  is  held perpendicular or  parallel  to  the 
diffusional direction. 
(4) 
68 (1918). 3 
dramatically to  magnetic fields. 
show a 2-3 fold increase i n  its viscosity when a 4000 oerstedmag- 
The viscosity of nematic materials responds 
T. Svedberg, Kolloid Z .  - 18, 54, lOl(1916); - 21, 19(1917); - 22,
For example, p-azoxyanisole can 
5 netic f ie ld  is applied. 
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(5) M. Miesowicz, Bull. Acad. Pol - A 228[1936). 
We are studying the effect  of a magnetic f ie ld  on 
cholesteric materials, but w i l l  also verify the reports on nematic 
materials. 
because we have experienced several delays in  the delivery of a 
specially constructed 6" electromagnet. 
Our critical experiments have not as yet been performed 
This magnet can be rotated 
i n  the horizontal plane and also be t i l t ed  into a vertical  plane 
t o  vary the applied f ie ld  direction on the liquid crystal. 
The l i terature  is  devoid of data f o r  cholesteric liquid 
crystals. 
pelargonate which shows the following phase transitions: 
Our primary study is being performed on cholesteryl 
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smectic --- c h o l e s t e r i c e l i q u i d  
In our work thus far,  we have designed a miniature 
fall ing bal l  viscometer which can be thennostated between the 
pole pieces of a magnet. 
ular or parallel  to the motion of the ba l l .  
The f i e ld  can be held either perpendic- 
For the diffusion studies, we have decided that self-  
diffusion should be performed with liquid crystalline materials 
prior to  the study of ionic diffusion. 
this is simply that  complex diffusion may par t ia l ly  destroy the 
molecular orientation of  the liquid crystalline phase thus com- 
plicating the interpretation of results. 
The primary reason for  
We have obtained C 1 4  
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cholesterol and have prepared C14 cholesteryl pelargonate. The 
diffusion of this  material t h r ~ ~ g h  C 1 2  c lh~ le s t eq l  pclarg~;;ate 
w i l l  be investigated using two techniques: 
(1) Microdensitometry of autoradiographs 
(2) Liquid scinti l lat ion counting of dissolved thin 
sections. 
Diffusion cells have been bui l t  for  the autoradiographic 
experiments and similar equipment is being bu i l t  fo r  the thin 
sectioning experiments. The autoradiographic equipment is so 
designed that we are able t o  study the diffusion of both a point 
and a l ine  source of the radioactive component through the non- 
radioactive bulk. 
provide an estimation of accuracy plus a method for  separating 
bulk diffusion from surface anomalies. 
A comparison of data using both techniques w i l l  
A l l  equipment may be used in  a magnetic field.  We believe 
that the diffusion experiments w i l l  enable us t o  work a t  higher 
f i e l d  strengths than those used for  the viscosity experiments be- 
cause of the smaller apparatus size.  This w i l l  permit the detemin- 
ation of threshhold values for magnetic f i e l d  orientation effects 
over a wider range of f i e ld  strengths than could be obtained solely 
w i t h  viscometric measurements. 
c c 
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Personnel 
. The work on the  behavior of liquid crystals i n  an 
e lec t r ic  f i e l d  is being conducted by Dr. S. Kusabayashi. 
T. Laronge is performing the work on diffusion and viscosity 
i n  liquid crystals. 
is D r .  M. M. Labes. 
M r .  
The principal investigator f o r  th i s  study 


Mechanisms for the effects of electric and magnetic fields on biological systems Semiannual status report, Jun. - Dec. 1967

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