
	Where results make sense

Topic: Isotactic

Related Topics

Concierge

Arachnoid

Globemallow

Alangalang

Women in the Victorian era

Frontinus

Siege of Fukuryuji

SC Bastia

Smolensk

In the News (Sun 15 Nov 09)

Northern Trust

Marvin Harrison

Peter Chernin

Gary Locke

Match Play

Penelope Cruz

Mickey Rourke

AR Rahman

Danny Boyle

Hugh Jackman

	Preparing isotactic stereoblock poly(lactic acid) - Patent 6538101
		A stereospecific poly(lactic acid) is isotactic poly(lactic acid) having a number average molecular weight ranging from 10,000 to 200,000 grams per mole, with, on average, an equal number of poly (R) and poly (S) blocks where each block contains an average of 5 to 50 monomer units.
		Isotactic stereoblock poly(lactic acid) having a number average molecular weight ranging from 10,000 to 200,000 grams per mole with, on average, an equal number of poly (R) and poly (S) blocks of equal average number of monomer units where each block contains an average of 9 to 50 monomer units.
		One embodiment herein, denoted the first embodiment, is directed to isotactic stereoblock poly(lactic acid) having a number average molecular weight ranging from 10,000 to 200,000 grams per mole, with, on average, an equal number of poly (R) and poly (S) blocks where each block contains an average of 5 to 50 monomer units.
	www.freepatentsonline.com /6538101.html (2233 words)

	HP-Trend (Site not responding. Last check: )
		In practice, it is important that the portion of the isotactic component (the isotacticity index) be at least 90%, in fibres at least 95 to 97%.
		Thus the most ingenious methods of polymerisation provide high-quality isotactic polypropylene, but at the same time have increased the demand for the atactic form, as there have been interesting ways of application with good perspectives of use found for it (permanent plastic cement, bitumen modifiers etc.).
		In the first group, the isotactic type (Figure 1a) the side methyl groups are always placed at one side of the main polymer chain, if we imagine it being spread in an ideal position, whereas in syndiotactic polypropylene (Figure 1b) the side methyl groups are regularly spread at both sides of the chain.
	www.hp-trend.cz /en/e_ti_pp.htm (1465 words)

	Isotactic (Site not responding. Last check: )
		Isotactic polymers refer to those polymers formed by branched monomers that have the characteristic of having all the branch groups on the same side of the polymeric chain[?].
		The monomers are all oriented in the same way: If we represent a monomer by AB then an isotactic polymer is AB-AB-AB-AB-AB-etc
		Besides Isotactism, there are other two types of stereoregularity frequently found in the scientific literature:
	www.ebroadcast.com.au /lookup/encyclopedia/is/Isotactic.html (86 words)

	Isotactic Definition \| Define Isotactic \| What Is It?
		A polymer is isotactic if all of the groups attched to the back bone are arranged in the same geometrical pattern.
		We hope you now understand the meaning of Isotactic.
		If you need any more information on this term, please don't hesitate to contact us.
	www.chemicalglossary.net /definition/947-Isotactic (85 words)

	Group 4 Metallocenes for Polymerization Reactions (Site not responding. Last check: )
		Isotactic polymers are characterized by having only one symmetry type of monomer while syndiotactic polymers have an alternating configuration of side groups.
		It was concluded that polymerization occurred by 1-2 cis addition with retention of the stereoconfiguration at the coordinated carbon atom.
		Although these soluble catalysts with stereoregular chiral ligands were shown to produce isotactic polypropylene, the much faster rates and improved catalyst stabilities obtained with methyl alumoxane could not yet be accounted for.
	courses.cm.utexas.edu /archive/Fall1997/CH380L/jg.html (2488 words)

	Mohan Srinivasarao Research Lab
		The syndiotactic PMMA wraps around the isotactic chain, forming a 9/1 double stranded helix, having an asymmetric unit consisting of 1 isotactic unit and 2 syndiotactic units.
		In these solvents, a viscosity drop is observed when dilute solutions of isotactic and syndiotactic PMMA are mixed.
		We mix the isotactic and syndiotactic PMMA in a stereocomplex forming solvent (DMF).
	www.tfe.gatech.edu /faculty/mohan/StereocomplexFibers.htm (645 words)

	Session 5
		If all the methyl groups lie on the same side of the chain, the polymer is called isotactic.
		Atactic polypropylene is a soft, rubbery polymer, while isotactic polypropylene is strong and hard with excellent resistance to stress, cracking, and chemical reaction.
		It is somewhat softer than the isotactic polymer, but also tough and clear.
	www.chemistry.wustl.edu /~edudev/Designer/session5.html (524 words)

	TxSpace at Texas A&M University Libraries: Item 1969.1/3061
		Isotactic polypropylene production from these systems depends highly on the size of these substituents.
		It is known that ansa-C2- symmetric metallocenes are good catalysts for isotactic polypropylene production, but in general, their synthesis suffers from the production of the meso Cs-stereoisomer of these catalysts, which generally produces only atactic polypropylene.
		Therefore, the meso stereoisomers must be removed and this is considered a loss of the material that increases the cost of the catalysts.
	txspace.tamu.edu /handle/1969.1/3061 (361 words)

	Chemistry Department
		We are studying the mechanism for the isotactic stereospecific polymerization of a-olefins such as 1-butene and 1-hexene by rigid, chiral zirconocene catalysts.
		These catalysts are unique in that they are the only homogeneous Ziegler-type catalysts to achieve highly isotactic polymerization.
		Our overall approach to understanding polymerization mechanism is characterization of polymer structure and correlation of structure with polymerization variables such as catalyst structure and polymerization conditions.
	www.chem.csi.cuny.edu /odian.htm (164 words)

	Giulio Natta - Biography
		isotactic, syndiotactic and di-isotactic polymers and linear non branched olefinic polymers and copolymers with an atactic (or sterically nonordered) structure.
		These studies, which were developed for industrial application in Montecatini's laboratories, led to the realisation of a thermoplastic material, isotactic polypropylene, which Montecatini were the first to produce on an industrial scale, in 1957, in their Ferrara plant.
		This product has been marketed successfully as a plastic material, by the name of Moplen, as a synthetic fibre, by the name of Meraklon, as a monofilament by the name of Merakrin and as packing film, by the name of Moplefan.
	nobelprize.org /nobel_prizes/chemistry/laureates/1963/natta-bio.html (744 words)

	Polypropylene Market Study Report - U.S. Adhesives Industry
		In isotactic polypropylene, all methyl groups are positioned on the same side of the polymer chain; in atactic polypropylene, however, the methyl groups have a random distribution.
		The isotactic isomer is a tough, crystalline polymer widely used for a variety of mechanical applications, such as the manufacturing of film and molding, but finds little use in adhesives.
		APP is used both as a primary polymer and a modifier, such as a replacement for micro-crystalline wax, in commodity hot melt adhesives.
	www.chemquest.com /store/polypropylene-us-adhesives.html (349 words)

	Polymers, Ball Valve, Plastic Valves, Valves, Piping Systems, Ball Check, Pipes, Foot Valve, Sampling Valve, Sight Flow ...
		Chemical resistance of ISOTACTIC PP is more than that of normal grade PP even at an elevated temperature.
		Isotactic polypropylene has got excellent heat resistance upto 120 deg.C as against 85-90 deg.C of normal grade PP.
		This grade is proven in steel industries for their application of hydrochloric acid containing ferrous and ferric chloride at an elevated temp.
	www.plastic-valves.com /Polymers.htm (472 words)

	Isotactic Polypropylene-Nanocomposites on the base of organic boehmite DISPERAL OS2 — Freiburger ...
		Isotactic Polypropylene-Nanocomposites on the base of organic boehmite DISPERAL OS2 — Freiburger Materialforschungszentrum (FMF)
		Isotactic Polypropylene-Nanocomposites on the base of organic boehmite DISPERAL OS2
		Organophilic boehmite filler were melt compounded with isotactic polypropylene to prepare novel iPP nanocomposites.
	www.fmf.uni-freiburg.de /projects/polymeric-materials/isotactic-polypropylene-nanocomposites-on-the-base-of-organic-boehmite-disperal-os2?set_language=en&cl=en (334 words)

	Polypropylene
		This is because the isotactic blocks will form crystals by themselves.
		But because the isotactic blocks are joined to the atactic blocks, the little hard clumps of crystalline isotactic polypropylene are tied together by soft rubbery tethers of atactic polypropylene, as you can see in the picture on the right.
		To be honest, atactic polypropylene would be rubbery without help from the isotactic blocks, but it wouldn't be very strong.
	www.pslc.ws /mactest/pp.htm (439 words)

	M A Y U R
		Isotactic polymer is immune to degradation and oxidization.
		Isotactic P.P. at ELEVATED temperature is more than normal grade P.P..
		Isotactic P.P. has excellent temperature resistance up to 120 °C against 80 ° C - 90 ° C of normal grade P.P. sotactic Grade P.P. is proven in
	www.mayurvalves.com (1328 words)

	Microporous membranes from isotactic polystyrene and syndiotactic polystyrene (US4927535)
		Microporous membranes from isotactic polystyrene and syndiotactic polystyrene
		This invention relates to novel semi-permeable isotropic or anisotropic microporous membranes fabricated from a mixture of isotactic polystyrene and syndiotactic polystyrene and a method of producing such membranes.
		A semi-permeable membrane comprising a thin isotropic or anisotropic microporous membrane consisting essentially of a mixture of isotactic polystyrene and syndiotactic polystyrene, wherein the ratio of isotactic polystyrene to syndiotactic polystyrene is such as to provide said membrane with properties sufficient for maintaining structural integrity under conditions of ultrafiltration and/or microfiltration.
	www.delphion.com /details?pn=US04927535__ (372 words)

	THERMALcrystallization rates for isotactic polystyrene (Site not responding. Last check: )
		Dear All Powerful and Mighty THERMAL: In the process of reviewing several articles relating to polystyrene, to be published in the Encyclopedia of Polymer Science and Technology, I became aware of a disturbing lack of basic information concerning isotactic polystyrene.
		In particular, there was very little information concerning the main difference between isotactic polystyrene and other forms of polystyrene (atactic and syndiotactic), which is the rate at which it crystallizes.
		For example, it was pointed out that syndiotactic polystyrene is a commercial product because of its rapid rate of crystallization, but that isotactic polystyrene has limited commercial use because of its slow rate of crystallization.
	www.egr.msu.edu /mailman-archives/thermal/2001-January/000312.html (226 words)

	M_Gomez
		In particular, isotactic polypropylene (iPP) is one of the most important commercial thermoplastics with excellent properties.The group at the Institute of Science and Technology of Polymers (ISTP), CSIC (Madrid, Spain) has extensive experience in the preparation and characterization of i-PP blends and composites.
		The isotactic polypropylene samples obtained by coalescence of their inclusion compounds show a very different crystallization behaviour.
		A significant increase in crystallinity and in crystallization rate is detected after confinement in the narrow CD channels due to the existence of some degree of order in the melt as a consequence of the extended and untangled nature of the polymeric chains.
	www.materialsworld.net /mwn/gomez.htm (735 words)

	polymerisation of alkenes
		That means that isotactic poly(propene) is quite strong either as a solid object or when it is drawn into fibres.
		It is formed as a waste product during the manufacture of isotactic poly(propene) and its uses are limited.
		However, the attractions aren't as strong as in isotactic poly(propene).
	www.chemguide.co.uk /organicprops/alkenes/polymerisation.html (1946 words)

	publications
		"Evaluation of the Reversible Contribution from the Reversing Heat Capacity in Isotactic Polystyrene." Thermochimica Acta, in press 01/06.
		"Heat Capacity Study of Isotactic Polystyrene: Dual Reversible Melting and Enthalpic Relaxation of Rigid Amorphous Phase." Macromolecules, 37(8), 2797-2806 (2004).
		"Simultaneous in-situ WAXS and SAXS Study of Crystallization and Melting of Metallocene Isotactic Poly(propylene)".
	www.tufts.edu /~pcebe/publications.html (1775 words)

	Crossover behaviour of dielectric relaxation in isotactic polystyrene: from stretched exponential decay to power law ...
		Dielectric loss was studied for the alpha -relaxation of isotactic polystyrene; the relaxation is associated with the micro-Brownian motion of polymer chains in the amorphous phase.
		It was also found that the relaxation undergoes a crossover from a stretched exponential decay to a power law decay as the relaxation proceeds.
		Crystallized isotactic polystyrene has a definite crossover time, while amorphous isotactic polystyrene undergoes the crossover through an intermediate region.
	stacks.iop.org /0953-8984/3/5451 (269 words)

	Early Stages of Crystallization in Isotactic Polypropylene
		At low degrees of undercooling there is a substantial gap between the appearance of a peak in the small-angle scattering, associated with electron density modulations, and the resolution of crystallites.
		This early growth in electron density has been analyzed in terms of a spinodal decomposition process and the stability limit of isotactic polypropylene determined for three different samples of varying molecular weight.
		The underlying physics of the early stages of crystallization are discussed and a number of scenarios eliminated; at high temperature Avrami kinetics are not observed whereas at low temperatures the structure in both the small-angle and wide-angle regimes grow contemporaneously following secondary nucleation.
	pubs.acs.org /cgi-bin/abstract.cgi/mamobx/2003/36/i10/abs/ma021373i.html (234 words)

	“Crystallization of Isotactic Polystyrene in Thin Films: A High Throughput Approach”
		Crystallization of Isotactic Polystyrene in Thin Films: A High Throughput Approach
		Very thin films of semi-crystalline polymers are increasingly being employed in coatings applications and there is a need to better understand how film thickness and crystallization conditions influence the crystalline morphology and resulting film properties.
		Since the parameter space governing this problem is large and the theoretical understanding of thin film crystallization is limited, we study a model polymer (isotactic polystyrene) using a combinatorial, high throughput methodology in order to identify the most salient phenomenological aspects of this problem.
	www.nist.gov /sigmaxi/Posters01/beers-abst.html (153 words)

	The BASF Team @ ISIS-ULP - Dr. Xinyuan Zhu, Post-Doctoral Researcher
		"On-line FTIR spectroscopic study of the disorientation of uniaxially stretched isotactic polypropylene upon heating"
		"In situ FTIR spectroscopic study of the conformational change of isotactic polypropylene during crystallization process"
		"In situ FTIR spectroscopic study of the regularity bands and partial-order melts of isotactic polypropylene"
	www-isis.u-strasbg.fr /BASF/zhu.html (1228 words)

	Isomerism - Stereoisomerism in Organic Chemistry GCE-AS-A2-K12 Stereoisomerizm Geometrical and Optical at Doc Brown's ...
		It tends to softer and more flexible (than the isotactic form, below) and is used for roofing materials, sealants and other weatherproof coatings.
		A crystalline regular structure form called isotactic poly(propene) in which all the side chain methyl groups have the same regular orientation along the carbon-carbon polymer chain.
		Its properties are similar to isotactic poly(propene) rather than the atactic form i.e.
	www.wpbschoolhouse.btinternet.co.uk /page07/isomerism2b.htm (6354 words)

Try your search on: Qwika (all wikis)