Module 3 : Classical Molecular Dynamics
Chapter 30 : Viscocity Of Polymeric Liquids Through Montecarlo Simulations
 

30.2. Polyethylene glycol (PEG)and Polypropylene glycol (PPG)

Polyethylene glycol (PEG) is an industrially important polyether compound (used in cosmetics, food and pharmaceuticals, water-based coatings, lubricants, dye carriers for paints, anti-static agents in textile manufacture and oral healthcare products) which often finds clinical applications. PEG is synonymous to polyethylene oxide (PEO) and polyoxyethylene (POE). Usually PEG refers to oligomers and polymers with molar mass less than 20,000 g/mol while PEO refers to polymers of molar mass more than 20,000 g/mol. On the other hand, POE is not characterized by any specific molar mass range. Although PEG and PEO with different molecular weights find use in different applications and have different physical properties (like viscosity) due to chain length effects, their chemical properties are nearly identical. PEG or PEO has the following structure, HOCH2-(CH2- O-CH2-)nCH2OH.
 
Polypropylene glycol (PPG) is the homo-polymer of propylene glycol, CH3-CHOH-CH2OH. PPG usually refers to the polymers of low to medium range molar mass polymer, with the end group as a hydroxyl group. Using the PEG and PPG as precursors, often random polymers are prepared such as poly(ethylene glycol-ran-propylene glycol) (≡ PEG-ran-PPG), which finds its use as a quenchant, lubricant and foam control agentand also as a surfactant. The PEG-ran-PPG has the structure H(-O-CH2-CH2-)x(O-CH(CH3)-CH2-)y(O-CH2-CH2-)zOH. The polymer is a liquid at room temperature facilitating its suitability to be used as a surfactant in various applications.
 

In this chapter, we intend to look into the bulk rheological properties of the PEG:PEG-ran-PPG system, since overall viscosity of the blend has a deterministic role in the formation and stability of the resulting film on drying. For this purpose, we have measured the dynamic viscosity of several blends at the mixing temperature of 1500C. In order to supplement the measured dynamic viscosities of the blend compositions, we have performed coarse-grained Monte Carlo simulations on these systems. Viscosity values have been obtained by integrating the calculated stress relaxation modulus G(t) function for each of the blend systems as well as of the pure components. The results show that there is a one-to-one correspondence between the measured and simulated bulk viscosities.