PMID- 23214601
OWN - NLM
STAT- PubMed-not-MEDLINE
DCOM- 20130524
LR  - 20121211
IS  - 1550-2376 (Electronic)
IS  - 1539-3755 (Linking)
VI  - 86
IP  - 4 Pt 1
DP  - 2012 Oct
TI  - Critical behavior of a nonpolar smectogen from high-resolution birefringence 
      measurements.
PG  - 041705
AB  - We report high-sensitivity and high-temperature resolution experimental data for 
      the temperature dependence of the optical birefringence of a nonpolar monolayer 
      smectogen 4-butyloxyphenyl-4'-decyloxybenzoate (10[over  ].O.4[over  ]) liquid 
      crystal by using a rotating-analyzer technique. The birefringence data cover 
      nematic and smectic-A phases of the 10[over  ].O.4[over  ] compound. The 
      birefringence data are used to probe the temperature behavior of the nematic 
      order parameter S(T) in the vicinity of both the nematic-isotropic (N-I) and the 
      nematic-smectic-A (N-SmA) transitions. For the N-I transition, from the data 
      sufficiently far away from the smectic-A phase, the average value of the critical 
      exponent beta describing the limiting behavior of S(T) is found to be 0.2507+/-0.0010, 
      which is in accordance with the so-called tricritical hypothesis, which predicts 
      beta=0.25 and excludes higher theoretical values. The critical behavior of S(T) at 
      the N-I transition is discussed in detail by comparing our results with the 
      latest reports in the literature and we conclude that by comparing with the 
      previously reported results, the isotropic internal field assumption by the 
      Vuks-Chandrasekhar-Madhusudana model is adequate to extract the critical behavior 
      of S(T) from the optical birefringence data. We observe that there is no 
      discontinuous behavior in the optical birefringence, signaling the second-order 
      nature of the N-SmA transition. The effect of the coupling between the nematic 
      and smectic-A order parameters on the optical birefringence near the N-SmA 
      transition is also discussed. In a temperature range of about 4K above and below 
      the N-SmA transition, the pretransitional evidence for the N-SmA coupling have 
      been detected. From the analysis of the optical birefringence data above and 
      below the N-SmA transition by means of various fitting expressions we test the 
      validity of the scaling relation lambda=1-alpha between the critical exponent lambda describing 
      the limiting behavior of the nematic order parameter and the specific heat 
      capacity exponent alpha. We then show that the temperature derivative of the nematic 
      order parameter S(T) near T(NA) exhibits the same power-law divergence as the 
      specific heat capacity with an effective critical exponent of 0.2303+/-0.0035.
FAU - Erkan, Selen
AU  - Erkan S
AD  - Department of Physics, Istanbul Technical University, 34469 Maslak, Istanbul, 
      Turkey.
FAU - Cetinkaya, Mehmetcan
AU  - Cetinkaya M
FAU - Yildiz, Sevtap
AU  - Yildiz S
FAU - Ozbek, Haluk
AU  - Ozbek H
LA  - eng
PT  - Journal Article
PT  - Research Support, Non-U.S. Gov't
DEP - 20121011
PL  - United States
TA  - Phys Rev E Stat Nonlin Soft Matter Phys
JT  - Physical review. E, Statistical, nonlinear, and soft matter physics
JID - 101136452
EDAT- 2012/12/12 06:00
MHDA- 2012/12/12 06:01
CRDT- 2012/12/11 06:00
PHST- 2012/06/28 00:00 [received]
PHST- 2012/12/11 06:00 [entrez]
PHST- 2012/12/12 06:00 [pubmed]
PHST- 2012/12/12 06:01 [medline]
AID - 10.1103/PhysRevE.86.041705 [doi]
PST - ppublish
SO  - Phys Rev E Stat Nonlin Soft Matter Phys. 2012 Oct;86(4 Pt 1):041705. doi: 
      10.1103/PhysRevE.86.041705. Epub 2012 Oct 11.