Faculty of Science - Mahidol University

Mahidol University Annual Research Abstracts, Vol. 33 329
EFFECT OF THE SURFACTANT COVERAGE ON
THE PREPARATION OF POLYSTYRENE-CLAY
NANOCOMPOSITES PREPARED BY MELT
INTERCALATION (NO. 870)
S. Limpanart 1,2 , S. Khunthon 2 , P. Taepaiboon 3 , P. Supaphol 3 , T.
Srikhirin 4,5,* , W. Udomkichdecha 1
, Y. Boontongkong6 .
1 Department of Materials Science, Faculty of Science,
Chulalongkorn University, Phayathai, Bangkok 10330,
Thailand; 2 Metallurgy and Materials Science Research Institute,
Chulalongkorn University, Phayathai, Bangkok 10330,
Thailand; 3 Petroleum and Petrochemical College,
Chulalongkorn University, Phayathai, Bangkok 10330,
Thailand; 4 Department of Physics, Faculty of Science, Mahidol
University, Phayathai, Bangkok 10400, Thailand; 5 Capability
Building Unit in Nanoscience and Nanotechnology, Faculty of
Science, Mahidol University, Phayathai, Bangkok 10400,
Thailand; 6 National Metal and Materials Technology Center,
National Science and Technology Development Agency,
Klongluang, Prathumthani 12120, Thailand.
Key words: nanocomposites, nanomaterials, polymers, clay,
polystyrene
The melt intercalation of polystyrene (PS) into organoclay
with varying the degree of surfactant coverage by melt intercalation
was investigated. The surface coverage of the organoclay was found
to play a major role in controlling the type of the final composites
formation. Two major types of composites were found depending
upon the surface treatment of the organoclay. They are conventional
composites and intercalated nanocomposites. At the high degree of
clay’s surface coverage, the conventional composite was obtained.
It is characterized by the micron size aggregated of the organoclay
particle. An intercalated nanocomposite was observed in the
organoclay with a lower surface coverage. The organoclay is
dispersed into a smaller stack along with the intercalation of
polystyrene into the organoclay interlayer. This is originated from
the affinity between the organoclay surface and a molten polystyrene.
(Material Letter, 59, 2292-2295 (2005)
ELECTROSPINNING OF POLYSTYRENE/POLY
(2-METHOXY-5 (2’ETHYLHEXYLOXY)-1,4-PHENY-
LENE VINYLENE) BLENDS (NO, 871)
Patcharaporn Wutticharoenmongkol 1 , Pitt Supaphol 1 , Toemsak
Srikhirin 2 , Teerakiat Kerdcharoen 2 and Tanakorn Osotchan 2
1 The Petroleum and Petrochemical College, Chulalongkorn
University, Soi Chula1 2, Phyathai Road, Pathumwan, Bangkok
10330, THAILAND; 2 Department of Physics, Faculty of Science,
Mahidol University, Rama 6 Road, Ratchathewi, Bangkok
10400, THAILAND.
Key words: electrospinning; polystyrene; poly(phenylene vinylene)
Ultrafine polystyrene (PS)/poly(2-methoxy-5-(2’ethylhexyloxy)-1,4-phenylene
vinylene) (MEHPPV) fibers were
successfully prepared by electrospinning of PS/MEH-PPV solutions
in chloroform, 1,2-dichloroethane, and tetrahydrofuran (THF). Three
concentrations of the solutions were prepared: 8.5, 16, and 23.5%
(w/v), with the compositional weight ratios between PS and MEH-
PPV being 7.5:1, 15:1, and 22.5:1, respectively. Smooth fibers only
observed from 23.5% (w/v) PS/MEH-PPV solution in chloroform.
Improvement in the electro-spinnability of 8.5% (w/v) PS/MEH-
PPV solution in chloroform was achieved by addition of an organic
salt, pyridinium formate (PF), or by addition of a minor solvent
with high dielectric constant value. The average fiber diameters of
the as-spun PS/MEH-PPV fibers were between 0.30 and 5.11 µm.
(Journal: Journal of Polymer Science, Part B, Polymer Physics,
43, 1881-1891 (2005))
ON THE ESTIMATION OF SOLAR ENERGETIC
PARTICLE INJECTION TIMING FROM ONSET
TIMES NEAR EARTH (NO. 872)
Alejandro Saiz, 1,2 , Paul Evenson 3 , David Ruffolo 1 , and John W.
Bieber 3
1 Department of Physics, Faculty of Science, Mahidol Univesity,
Bangkok 10400, Thailand; 2 Department of Physics, Faculty of
Science, Chulalongkorn University, Bangkok 10330, Thailand;
3 Bartol Research Institute, University, Delaware, Newark DE
19716.
Key words : interplanetary medium,methods numerical, solar
terrestrial relations
We examine the accuracy of a common technique for
estimating the stat time of solar energetic particle injection based
on a linear fit to the observed onset time versus 1/(particle velocity).
This is based on a concept that the first arriving particles move
directly along the magnetic field with no scattering. We check this
by performing numerical simulations of the transport of solar protons
between 2 and 2000. MeV from the Sun to the Earth, for several
assumptions regarding interplanetary scattering and the duration of
particle injection, and by analyzing the results using the inverse
velocity fit. We find that, in most cases, the onset times align close
to a straight line as a function of inverse velocity. Despite this, the
estimate injection time can be in error by several minutes. Also, the
estimated path length can deviate greathy from the actual path length
along the interplanetary magnetic field. The major difference
between the estimazted and actual path lengths implies that the first
arriving particles cannot be viewed as moving directly along the
interplanetary magnetic field.
(The Astrophysical Journal, 626:1131-1137, 2005 June 20)
RELATIVISTIC SOLAR NEUTRONS AND PROTONS
ON 28 OCTOBER 2003. (NO. 873)
John W. Biever 1 , John Clem 1 , Paul Evenson 1 , Roger Pyle 1 , David
Ruffolo 2 , Alejandro Saiz 3
1 Bartol Research Institute, University of Delaware, Newark,
Delaware, USA.; 2 Department of Physics Mahidol University,
Bangkok, Thailand.; 3 Department of Physics, Chulalongkorn
University, Bangkok, Thailand.
The solar cosmic ray event associated with the X17.2 class
flare of 28 October 2003. was unusal in several respects (1) Several
high-latitude neutron monitors observed a large, highly anisotropic
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