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Studies of cyclic and linear poly(dimethyl siloxanes): 14. Particle scattering functions

Authors
Journal
Polymer
0032-3861
Publisher
Elsevier
Publication Date
Volume
25
Issue
3
Identifiers
DOI: 10.1016/0032-3861(84)90289-1
Keywords
  • Cyclic Poly(Dimethyl Siloxane)
  • Linear Poly(Dimethyl Siloxane)
  • Cyclic Polymethylene
  • Monte Carlo Calculations
  • Particle Scattering Functions
  • Neutron Scattering

Abstract

Abstract Particle scattering functions P( Q) (where Q represents the wave vector), have been calculated using a Monte Carlo method for cyclic and linear poly(dimethyl siloxanes) (PDMS) containing up to 100 skeletal bonds. A maximum is found in the Kratky plot at u (=Q〈s 2〉 1 2 )≈2.0 for cyclic PDMS (with root-mean-square radii of gyration 〈s 2〉 1 2 ) and this is in satisfactory agreement with the analytical calculations of Casassa and of Burchard and Schmidt. In addition, other clearly-defined maxima are found at u≈5.0 for PDMS ring molecules with less than ≈40 skeletal atoms. These maxima are believed to be characteristic of small cyclic molecules as they are also predicted for small polymethylene rings. Comparisons are made with experimental small-angle neutron scattering (SANS) data for cyclic and linear PDMS. A single maximum in the experimental Kratky plot at u≈2.0 is found for PDMS ring molecules with an average of 550 skeletal atoms. The experimental data for cyclic PDMS are in better agreement with the Monte Carlo calculations of P( u) than with analytical predictions up to u≈2.0.

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