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Topic: Polydispersity index

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Polydispersity

Living polymerization

Polymerization

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	[No title] (Site not responding. Last check: 2007-09-11)
		The disclosed process and article of manufacture are based on a low density polyethylene of narrow molecular weight distribution having a melt index of 2.0 to 4.0 dg/min, a swell ratio of 1.2 to 1.35, an annealed density of 0.91 to 0.93-g/cc, and a polydispersity index of between about 6 and about 9.
		The term "broad molecular weight distribution" means broad molecular weight distribution as reflected, for instance, in the polydispersity index alone, and/or by the aforementioned swell ratio, which characterizes the second component.
		Polydispersity Index (Mw/Mn) is obtained by size- exclusion chromatography on a Waters 1500C gel permeation chromatograph equipped with the standard refractometer detector and a Viscotek 150R differential viscometer system.
	www.wipo.int /cgi-pct/guest/getbykey5?KEY=98/37138.980827&ELEMENT_SET=DECL (5209 words)

	Pigment Milling — Monitoring Particle Size Using Dynamic Light Scattering Techniques (Site not responding. Last check: 2007-09-11)
		The z-average diameter and polydispersity index values are calculated from the cumulants analysis as described in the International Standard on DLS ISO13321.
		The z-average diameters and polydispersity index values obtained from three repeat measurements are shown together with the standard deviations (in brackets).
		The z-average diameter and polydispersity index values obtained for the sample removed after 3 hours of milling are not consistent with the other results.
	www.azom.com /details.asp?ArticleID=2724 (1395 words)

	[No title] (Site not responding. Last check: 2007-09-11)
		According to the present invention, fumaryl chloride and propylene glycol are reacted in the presence of potassium carbonate, which serves as a proton scavenger, to produce bis (propyl fumarate).
		polydispersity index and reduced the maximum molecular weight of the ultimate P (PF) product that can be obtained.
		In addition, by varying the molecular weight of the poly (propylene fumarate) a composite material having desired strength and modulus characteristics, including that which approximates the physical characteristics of human trabecular bone, is produced.
	www.wipo.int /cgi-pct/guest/getbykey5?KEY=99/52469.000323&ELEMENT_SET=DECL (3719 words)

	Solubilizing Poorly Soluble Antimycotic Agents by Emulsification via a Solvent-Free Process
		At the higher concentration of 10.0 mg/mL, the particle size was reduced, being 223 nm with a polydispersity index of 0.110 at 10 mg/mL (cycle 15).
		Ketoconazole was processed the same way as itraconazole (ie, producing the ketoconazole nanosuspension first [yielding a PCS diameter of 750 nm and a polydispersity index of 0.380], admixing the Lipofundin MCT 20% to the nanosuspension, and further homogenizing the predispersion to yield the drug-loaded emulsion).
		This increase in diameter was accompanied by a simultaneous increase in the polydispersity index.
	www.aapspharmscitech.org /view.asp?art=pt050124&pdf=yes (3428 words)

	Synthesis of poly(propylene fumarate) by acylation of propylene glycol in the presence of a proton scavenger - Patent ...
		Fumaryl chloride and propylene glycol are reacted in the presence of potassium carbonate.
		According to the present invention, fumaryl chloride and propylene glycol are reacted in the presence of potassium carbonate, which serves as a proton scavenger, to produce bis(propyl fumarate).
		Equally importantly, the preferred method yields P(PF)s having polydispersity indices, or PI (PI=M.sub.w /M.sub.n where M.sub.w is the weight average molecular weight and M.sub.n is the number average molecular weight), less than 2 and more preferably approximately 1.
	www.freepatentsonline.com /6355755.html (4063 words)

	Number Avearage and Weight Average Molecular Weight
		Using strings of varying lengths to represent polymers of varying degrees of polymerization, students are able to calculate the number average molecular weight, the weight average molecular weight and the polydispersity index for a "sample" with a distribution of chain lengths.
		The polydispersity index is the number average molecular weight divided by the weight average molecular weight.
		It is of interest to note that even though this distribution appears to be broad, it yields a polydispersity index very close to 1.0.
	www.pslc.ws /macrog/activity/mwstrin.htm (273 words)

	Hydrocarbon compositions containing polyolefin graft polymers - Patent 4764304
		A lubricating oil composition as claimed in claim 1 wherein said amine is a secondary amine containing, as a nucleus, a morpholine, a piperazine, a pyrrolidine, or a phenothiazine.
		Molecular weight distribution of the useful polymers is preferably narrow viz a polydispersity index of typically less than 15, preferably 1.5-10, say about 2.2.
		In this example which describes the best mode presently known, the charge EPM polymer is the Epsyn brand of polymer of molecular weight M.sub.n of 135,000, of polydispersity index of 1.6, and containing 55 mole % of units derived from ethylene and 45 mole % of units derived from propylene.
	www.freepatentsonline.com /4764304.html (3402 words)

	Behaviroal Objectives, Chapter 4 (Site not responding. Last check: 2007-09-11)
		Describe and discuss the polydisperse and/or polymolecular nature of polysaccharides with respect to their purification, fractionation, homogeneity, and/or structural analysis.
		Given analytical information about a modified polysaccharide, calculate the DS or MS as appropriate; or given the DS, calculate the number of substituent groups per polysaccharide unit of given length.
		When given the number and molecular weight of two or three groups of molecules, be able to calculate Mw, Mn, and polydispersity index (see slide 72 in Dr. Yao's starch lecture).
	www.cfs.purdue.edu /Class/F&n630/objch4.htm (310 words)

	Process Control Rheometer PCR-620 Series
		When measuring the Melt Flow Index, the viscosity is measured at two values of the stress, and the power law index is calculated to give the true viscosity.
		The hydrostatic pressure in the die is measured by P3 and its output used to control the pressure to a given but variable set point, thereby suppressing the volatilization of dissolved gases within the polymer, e.g.
		Melt Index, Alpha, and polydispersity Index data are updated approximately every two to three minutes.
	www.laboratorynetwork.com /Content/ProductShowcase/product.asp?DocID={745131B4-3BC4-11D4-8C3E-009027DE0829}&VNETCOOKIE=NO (628 words)

	DelSite Biotechnologies Inc. Scientific Publications
		The weight average molecular weight, radius of gyration, and polydispersity index of the GelSite polymer were determined to be approximately 400 kDa, 100 nm, and 1.5, respectively.
		A molecular weight of approximately 24 kDa and a polydispersity of 1.0 were determined for the hGH.
		In addition, concentrations of GelSite by refractive index detection and concentrations of protein by refractive index and UV were determined for each formulation.
	www.delsite.com /newfiles/aaps_stroud_may_04.html (342 words)

	GPC
		Since synthetic polymers and many natural polymers as well, have a distribution of molecular weights, the ratio of these two averages, the polydispersity index (PDI), sometimes called the molecular weight distribution (MWD), of these two averages have classically defined the breadth of the distribution.
		While GPC has its greatest value for measuring the molecular weight and polydispersity of synthetic polymers, a closely related method, high-performance liquid chromatography, HPLC, is more useful for polymers containing functional groups, such as proteins and pharmaceutical polymers containing special active groups.
		The refractive index detector measures the change in refractive index as the concentration of polymer in the solution changes, and is usually operated on some type of differential refractive index method or Fresnel refraction.
	www.polyacs.org /nomcl/pmse.gpc.html (940 words)

	Macromolecular Nomenclature Note No. 12
		Synthesis of well-defined polymers and copolymers with predetermined molecular weights, low polydispersities, precisely controlled end group functionalities and chain topologies is the ultimate target of preparative polymer chemistry.
		The polydispersity index depends on the relative reactivities, the proportion of the species and rates of exchange.
		Thus, polydispersities cannot be used as the only criterion of livingness.
	www.polyacs.org /nomcl/mnn12.html (1942 words)

	Vasana Maneeratana - UF Journal of Undergraduate Research Paper
		The purpose of this experiment is to be able to clearly evaluate the role of the polarity of the solution in a dispersion polymerization with poly (Styrene-co-Diethyl (aminoethyl) methacrylate).
		Measuring the sizes and polydispersity indexes by varying the volume percentage of the ethanol and water mixture will test the hypothesis.
		The polydispersity index was calculated from the data obtained in the Coulter Laser Particle Size Analyzer.
	www.clas.ufl.edu /jur/200209/papers/paper_maneeratana.html (2133 words)

	JCE 2001 (78) 554 [Apr] Molecular Weight Averages and Polydispersity of Polymers
		In this paper, we give a simple statistical argument to show that the polymer polydispersity index, the ratio of the weight-average molecular weight (WAMW) to the number-average molecular weight (NAMW), is directly related to the standard deviation of the polymer molecular weight distribution.
		Therefore, the polydispersity index can be used as a measure of the width of the molecular weight distribution, as addressed in textbooks.
		This argument should help students to understand the physical meaning of the polydispersity index.
	jchemed.chem.wisc.edu:8000 /journal/issues/2001/Apr/abs554.html (225 words)

	Liposomes — Size and Zeta Potential Characterisation of Anionic and Cationic Liposomes Uisng the Zet
		This table shows the z-average diameters (the mean diameters based upon the intensity of scattered light), the polydispersity index (an estimate of the width of the distribution) and the mean zeta potential values obtained for the various liposome samples.
		The z-average diameters in nm, polydispersity index values and zeta potentials in mV of various anionic liposomes prepared in PBS.
		The z-average diameters in nm, polydispersity index values and zeta potentials in mV of various cationic liposomes prepared in PBS.
	www.azonano.com /details.asp?ArticleID=1220 (1266 words)

	[No title] (Site not responding. Last check: 2007-09-11)
		Title : Synthesis and Reactions of Strained Molecules and Polymers Abstract : Professor Kenneth Shea, of the Department of Chemistry at the University of California, Irvine, is supported by the Organic Synthesis Program for his studies of the synthesis and reactions of strained molecules and polymers.
		Alkyl boranes initiate the polymerization of dimethylsulfoxonium methylide, resulting in the formation of perfectly linear polymethylene with an extremely narrow polydispersity index.
		Adjustment of the initial ratio of ylide to alkyl borane permits control of the molecular weight of the resulting polymethylene, while chemical transformations of the carbon-boron bonds of polyhomologated alkyl boranes allow the introduction of a variety of terminal functionalities.
	www.cs.utexas.edu /users/yguan/NSFAbstracts/Abstracts/MPS/CHE.MPS.a9617475.txt (311 words)

	GC/MS at NDE Analytical - Expert chemical analysis and problem solving
		The average pore size of the column packing determines the molecular size range of the sample.
		The weight average (Mw), number average (Mn), the Z-average (Mz) as well as the polydispersity index (PDI) are provided for each analyzed sample.
		Information about additives that absorb in the UV-Vis region of the spectrum can be provided by recording the spectrum for the appropriate peak using the PDA detector.
	www.ndeanalytical.com /AnalyticalServices/GPC/GPC.html (263 words)

	polydispersity (Site not responding. Last check: 2007-09-11)
		In general terms: Low polydispersity is good, high polydispersity is bad for high...
		Kimura, and VC Hascall Polydispersity of proteoglycans synthesized...
		With approximately $425 million in HPLC sales, Waters is far and away the industry leader--with sales greater than twice that of our nearest competitor--and the only company focused primarily on HPLC.
	www.chemindustry.net /chemnames/P/polydispersity.html (278 words)

	The Society of Rheology: 69th Annual Meeting (Oct 1997) Abstract of Paper
		It is well recognized that the relationship between viscosity and shear rate is sensitive to the polydispersity and they play a critical role in the polymer processability.
		When a logarithmic-normal distribution function was used to characterize molecular weight distribution, we found an analytical solution for the relationship between shear viscosity, polydispersity index and weight average molecular weight.
		We found a linear relationship between the flow rate and the polydispersity index.
	www.rheology.org /sor97a/abstract.asp?PaperID=67 (267 words)

	[No title] (Site not responding. Last check: 2007-09-11)
		It was found that the polydispersity index (PI) of poly(methyl methacrylate) (PMMA) synthesized by using RATRP with bipyridine as ligand was as narrow as 1.08, but the polymerization induction time was quite long.
		When the N,N-dimethylformamide was used to replace the acetonitrile, the RATRP rate of MMA is faster and the PI of PMMA is narrower.
		It is evident that the possibility of conventional free radical polymerization of MMA in RATRP due to the decomposition of AIBN could be neglected.
	www.elsevier.com /cdweb/journals/00143057/articles/37/10/S001430570100078.abstract.en (164 words)

	Refractive Index Detector (Site not responding. Last check: 2007-09-11)
		The RI-2000L Differential Refractive Index Detector series offers the sensitivity, stability and reproducibility required for optimum RI detection.
		Average, Z Average, Z+1 Average, Viscosity Average molecular weights and Polydispersity index).
		The progressive electronic and mechanical design result in a detector with exceptional sensitivity, ultra-low noise level, the highest degree of baseline stability, and lowest service.
	www.laballiance.com /catalog/d6.htm (375 words)

	Nanopicture of the Day - Nanoparticle Light Dispersion - August 11, 2004
		Nearly monodisperse nanoparticles have been synthesized based on a naturally occurring polymer of hydropropylcellulose (HPC) using precipitation polymerization method.
		It is found that when the polydispersity index value of the HPC nanoparticles is less than 1.10, the HPC particles can self-assemble into an ordered structure, displaying bright colors.
		UV-visible spectroscopy reveals that the color shifts to a lower wavelength as the interparticle distance decreases following the Bragg diffraction equation.
	www.nanopicoftheday.org /2004Pics/August2004/11Nanodispersion.htm (163 words)

	Problem Set 1 (Site not responding. Last check: 2007-09-11)
		A polydisperse sample of polystyrene is prepared by mixing three monodisperse samples in the following proportions: 1 g of 10,000 molecular weight, 2 g of 50,000 molecular weight and 2 g of 1,000,000 molecular weight.
		Using this information determine the following: (a) number-average molecular weight; (b) weight-average molecular weight; (c) z-average molecular weight; and (d) polydispersity index.
		A polymer is fractionated and is found to have a molecular-weight distribution shown below.
	www.chemeng.ucla.edu /che112/ProblemSets/pset1/set1.html (160 words)

	Homework3 (Site not responding. Last check: 2007-09-11)
		If in this sample of polycarbonate the mole fraction of species of size x-mer, N(x), is proportional to 1/x, calculate the polydispersity index of the sample..
		Calculate xn, xw, and the polydispersity (Q) at P=0.5, 0.9, 0.95, 0.99.
		Assume a linear relationship between retention time and molecular weight and that the MWDs can be approximated with the data on the given tables.
	www.colorado.edu /che/CLASSES/Polymers/Homework3.html (458 words)

	Summer Research Project in Chemistry, Bucknell University
		Atom transfer radical polymerization (ATRP), as an example, is used in our labs as an alternative, synthetically less demanding procedure than traditional anionic polymerization.
		By employing 9-bromoanthracene (a) and its derivatives as ATRP initiators, we have successfully produced polymers of a low polydispersity index (PDI) and possessing near quantitative flourene labeling (c).
		This project is in the initial stages and needs further work to fully characterize the system.
	www.bucknell.edu /Academics/Colleges_Departments/Academic_Departments/Chemistry/Summer_Research_Opportunities/Tillman_Summer_Project.html (500 words)

	THE UNIVERSITY OF TOLEDO (Site not responding. Last check: 2007-09-11)
		a) Explain the polydispersity index (PI) of a polymer.
		b) Sketch the molecular weight distribution for polydispersity index values of PI = 1, PI = 2 and PI = 4 (15 pts)
		c) Which type of polymers can attain a polydispersity index value of one.
	bioe.eng.utoledo.edu /adms_staffs/akkus/BIOE2200-HW5.htm (235 words)

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