ASTM D4001-20

Standard Test Method for Determination of Weight-Average Molecular Weight of Polymers by Light Scattering

SIGNIFICANCE AND USE
4.1 The weight-average molecular weight is a fundamental structure parameter of polymers, which is related to many physical properties of the bulk material, such as its rheological behavior. In addition, knowledge of the weight-average molecular weight, together with knowledge of the number-average molecular weight from osmometry, provides a useful measure of the breadth of the molecular-weight distribution.  
4.2 Other important uses of information on the weight-average molecular weight are correlation with dilute-solution or melt-viscosity measurements and calibration of molecular-weight standards for use in liquid-exclusion (gel-permeation) chromatography.  
4.3 To the extent that the light-scattering photometer is appropriately calibrated, light scattering is an absolute method and is therefore be applied to nonionic homopolymers that have not previously been synthesized or studied.
SCOPE
1.1 This test method describes the test procedures for determining the weight-average molecular weight Mw  of polymers by light scattering. It is applicable to all nonionic homopolymers (linear or branched) that dissolve completely without reaction or degradation to form stable solutions. Copolymers and polyelectrolytes are not within its scope. The procedure also allows the determination of the second virial coefficient, A2, which is a measure of polymer-solvent interactions, and the root-mean-square radius of gyration (s2)1/2, which is a measure of the dimensions of the polymer chain.  
1.2 The molecular-weight range for light scattering is, to some extent, determined by the size of the dissolved polymer molecules and the refractive indices of solvent and polymer. A range frequently stated is 10,000 to 10,000,000, is often extended in either direction with suitable systems and by the use of special techniques.  
1.2.1 The lower limit to molecular weight results from low levels of excess solution scattering over that of the solvent. The greater the specific refractive increment dn/dc (difference in refractive indices of solution and solvent per unit concentration), the greater the level of solution scattering and the lower the molecular weight that shall be determined with a given precision.  
1.2.2 The upper limit to molecular weight results from the angular dependence of the solution scattering, which is determined by the molecular size. For sufficiently large molecules, measurements must be made at small scattering angles, which are ultimately outside the range of the photometer used.  
1.3 The values stated in SI units are to be regarded as standard.  
1.4 This standard does not purport to address all of the safety concerns, if any, associated with its use. It is the responsibility of the user of this standard to establish appropriate safety, health, and environmental practices and determine the applicability of regulatory limitations prior to use.
Note 1: There is no known ISO equivalent to this standard.  
1.5 This international standard was developed in accordance with internationally recognized principles on standardization established in the Decision on Principles for the Development of International Standards, Guides and Recommendations issued by the World Trade Organization Technical Barriers to Trade (TBT) Committee.

General Information

• Status: Published
• Publication Date: 30-Jun-2020
• ICS: 83.080.01 - Plastics in general
• Technical Committee: D20 - Plastics
• Drafting Committee: D20.70 - Analytical Methods

Standards Content (Sample)

This international standard was developed in accordance with internationally recognized principles on standardization established in the Decision on Principles for the
Development of International Standards, Guides and Recommendations issued by the World Trade Organization Technical Barriers to Trade (TBT) Committee.
Designation: D4001 − 20
Standard Test Method for
Determination of Weight-Average Molecular Weight of
1
Polymers by Light Scattering
This standard is issued under the fixed designation D4001; the number immediately following the designation indicates the year of
original adoption or, in the case of revision, the year of last revision.Anumber in parentheses indicates the year of last reapproval.A
superscript epsilon (´) indicates an editorial change since the last revision or reapproval.
1. Scope* priate safety, health, and environmental practices and deter-
mine the applicability of regulatory limitations prior to use.
1.1 This test method describes the test procedures for
determining the weight-average molecular weight M of poly-
NOTE 1—There is no known ISO equivalent to this standard.
w
mers by light scattering. It is applicable to all nonionic
1.5 This international standard was developed in accor-
homopolymers (linear or branched) that dissolve completely
dance with internationally recognized principles on standard-
without reaction or degradation to form stable solutions.
ization established in the Decision on Principles for the
Copolymers and polyelectrolytes are not within its scope. The
Development of International Standards, Guides and Recom-
procedure also allows the determination of the second virial
mendations issued by the World Trade Organization Technical
coefficient, A , which is a measure of polymer-solvent
2
Barriers to Trade (TBT) Committee.
interactions, and the root-mean-square radius of gyration
2 1/2
(s ) , which is a measure of the dimensions of the polymer
2. Referenced Documents
chain.
2
2.1 ASTM Standards:
1.2 The molecular-weight range for light scattering is, to
IEEE/ASTMSI-10American National Standard for Use of
some extent, determined by the size of the dissolved polymer
theInternationalSystemofUnits(SI):TheModernMetric
molecules and the refractive indices of solvent and polymer.A
System
range frequently stated is 10,000 to 10,000,000, is often
extended in either direction with suitable systems and by the
3. Terminology
use of special techniques.
3.1 Definitions—Units, symbols, and abbreviations are in
1.2.1 The lower limit to molecular weight results from low
accordance with IEEE/ASTMSI-10.
levelsofexcesssolutionscatteringoverthatofthesolvent.The
greater the specific refractive increment dn/dc (difference in
4. Significance and Use
refractive indices of solution and solvent per unit
concentration), the greater the level of solution scattering and 4.1 The weight-average molecular weight is a fundamental
structure parameter of polymers, which is related to many
the lower the molecular weight that shall be determined with a
given precision. physical properties of the bulk material, such as its rheological
behavior. In addition, knowledge of the weight-average mo-
1.2.2 The upper limit to molecular weight results from the
angular dependence of the solution scattering, which is deter- lecular weight, together with knowledge of the number-
average molecular weight from osmometry, provides a useful
mined by the molecular size. For sufficiently large molecules,
measurements must be made at small scattering angles, which measure of the breadth of the molecular-weight distribution.
are ultimately outside the range of the photometer used.
4.2 Other important uses of information on the weight-
average molecular weight are correlation with dilute-solution
1.3 The values stated in SI units are to be regarded as
or melt-viscosity measurements and calibration of molecular-
standard.
weight standards for use in liquid-exclusion (gel-permeation)
1.4 This standard does not purport to address all of the
chromatography.
safety concerns, if any, associated with its use. It is the
responsibility of the user of this standard to establish appro- 4.3 To the extent that the light-scattering photometer is
appropriately calibrated, light scattering is an absolute method
1
This test method is under the jurisdiction ofASTM Committee D20 on Plastics
and is the direct responsibility of Subcommittee D20.70 on Analytical Meth-
2
ods.70.05). For referenced ASTM standards, visit the ASTM website, www.astm.org, or
CurrenteditionapprovedJuly1,2020.PublishedJuly2020.Originallyapproved contact ASTM Customer Service at [e-mail]. For Annual Book of ASTM
in 1981. Last previous edition approved in 2013 as D4001-13. DOI: 10.1520/ Standards volume information, refer to the standard’s Document Summary page on
D4001-20. the ASTM website.
*A Summary of Changes section appears at the end of this standard
Copyright © ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959. Uni
...

This document is not an ASTM standard and is intended only to provide the user of an ASTM standard an indication of what changes have been made to the previous version. Because
it may not be technically possible to adequately depict all changes accurately, ASTM recommends that users consult prior editions as appropriate. In all cases only the current version
of the standard as published by ASTM is to be considered the official document.
Designation: D4001 − 13 D4001 − 20
Standard Test Method for
Determination of Weight-Average Molecular Weight of
1
Polymers Byby Light Scattering
This standard is issued under the fixed designation D4001; the number immediately following the designation indicates the year of
original adoption or, in the case of revision, the year of last revision. A number in parentheses indicates the year of last reapproval. A
superscript epsilon (´) indicates an editorial change since the last revision or reapproval.
1. Scope*
1.1 This test method describes the test procedures for determining the weight-average molecular weight M of polymers by light
w
scattering. It is applicable to all nonionic homopolymers (linear or branched) that dissolve completely without reaction or
degradation to form stable solutions. Copolymers and polyelectrolytes are not within its scope. The procedure also allows the
determination of the second virial coefficient, A , which is a measure of polymer-solvent interactions, and the root-mean-square
2
2 1/2
radius of gyration (s ) , which is a measure of the dimensions of the polymer chain.
1.2 The molecular-weight range for light scattering is, to some extent, determined by the size of the dissolved polymer
molecules and the refractive indices of solvent and polymer. A range frequently stated is 10,000 to 10,000,000, is often extended
in either direction with suitable systems and by the use of special techniques.
1.2.1 The lower limit to molecular weight results from low levels of excess solution scattering over that of the solvent. The
greater the specific refractive increment dn/dc (difference in refractive indices of solution and solvent per unit concentration), the
greater the level of solution scattering and the lower the molecular weight that shall be determined with a given precision.
1.2.2 The upper limit to molecular weight results from the angular dependence of the solution scattering, which is determined
by the molecular size. For sufficiently large molecules, measurements must be made at small scattering angles, which are ultimately
outside the range of the photometer used.
1.3 The values stated in SI units are to be regarded as standard.
1.4 This standard does not purport to address all of the safety concerns, if any, associated with its use. It is the responsibility
of the user of this standard to establish appropriate safety safety, health, and healthenvironmental practices and determine the
applicability of regulatory limitations prior to use.
NOTE 1—There is no known ISO equivalent to this standard.
1.5 This international standard was developed in accordance with internationally recognized principles on standardization
established in the Decision on Principles for the Development of International Standards, Guides and Recommendations issued
by the World Trade Organization Technical Barriers to Trade (TBT) Committee.
2. Referenced Documents
2
2.1 ASTM Standards:
IEEE/ASTM SI-10 American National Standard for Use of the International System of Units (SI): The Modern Metric System
3. Terminology
3.1 Definitions—Units, symbols, and abbreviations are in accordance with IEEE/ASTM SI-10.
4. Significance and Use
4.1 The weight-average molecular weight is a fundamental structure parameter of polymers, which is related to many physical
properties of the bulk material, such as its rheological behavior. In addition, knowledge of the weight-average molecular weight,
together with knowledge of the number-average molecular weight from osmometry, provides a useful measure of the breadth of
the molecular-weight distribution.
1
This test method is under the jurisdiction of ASTM Committee D20 on Plastics and is the direct responsibility of Subcommittee D20.70 on Analytical Methods.70.05).
Current edition approved Nov. 1, 2013July 1, 2020. Published November 2013July 2020. Originally approved in 1981. Last previous edition approved in 2006 as
D4001-93 (2006).-13. DOI: 10.1520/D4001-13.10.1520/D4001-20.
2
For referenced ASTM standards, visit the ASTM website, www.astm.org, or contact ASTM Customer Service at [e-mail]. For Annual Book of ASTM Standards
volume information, refer to the standard’s Document Summary page on the ASTM website.
*A Summary of Changes section appears at the end of this standard
Copyright © ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959. United States
1

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D4001 − 20
4.2 Other important uses of information on the weight-average molecular weight a
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