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Understand Gaussian chain structures and form factors for polymer systems, including Debye function application, single-chain form factors, and various polymer chain architectures. Learn to calculate scattering cross-sections for modeling polymeric systems.
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Chapter 28 – FORM FACTORS FOR POLYMER SYSTEMS 28:1. THE DEBYE FUNCTION FOR GAUSSIAN CHAINS 28.2. SINGLE-CHAIN FORM FACTOR FOR GAUSSIAN CHAINS 28.3. OTHER POLYMER CHAIN ARCHITECTURES
28:1. THE DEBYE FUNCTION FOR GAUSSIAN CHAINS Gaussian probability distribution: Inter-monomer mean square distance: Form factor for Gaussian chains: Use the identity: Form factor: The Debye function: Radius of gyration:
28.2. SINGLE-CHAIN FORM FACTOR FOR GAUSSIAN CHAINS Gaussian probability distribution: Gaussian chains with excluded volume: Form factor with excluded volume: Form factor: Continuous limit: Define the Incomplete Gamma function: Final result:
A i C j B P(Q) 1 j F(Q) 1 N E(Q) 28.3. OTHER POLYMER CHAIN ARCHITECTURES Form factor: Form factor amplitude: Propagation factor: Case of a triblock copolymer:
SCATTERING CROSS SECTION Scattering cross section (cm-1): Where: (N/V) is the particle (or polymer) number density f is the particle volume fraction VP is the particle (or polymer) volume Dr2 is the contrast factor P(Q) is the form factor SI(Q) is the structure factor
COMMENTS -- Form factors for polymers are mass fractals. -- Their calculation is needed for modeling of polymeric systems of various architectures.