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All Answers (5)

1st Jan, 2014

Kathirvel Ganesan

German Aerospace Center (DLR)

Hi,

PEG-PPG-PEG is a triblock copolymer. It has a block-wise distribution of polymer units in the structure (shown in the link - mentioned by you). For example: PEG - x times is one polymer block; PPG - y times is another polymer block; PEG - z times is again a new polymer block. These blocks are linked together forming triblock copolymer.

Poly(ethylene glycol-ran-propylene glycol) is a polymer which has the random distribution or Bernoullian distribution of ethylene glycol and propylene glycol. Thats the reason why the name has the representation "-ran-" connecting the two monomers. Hope it helps.

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1st Jan, 2014

Alexander Tolstov

National Academy of Sciences of Ukraine

The structural feature of PEG-PPG-PEG block copolymer is a sequential bonding the corresponding polymer chains {poly(ethylene glycol) chain bonded with poly(propylene glycol) chain followed by bonding with another poly(ethylene glycol) chain). This is resulted in characteristics of the block copolymer as excellent surfactant (terminal polar PEG fragments and nonpolar PPG fragment in the center). According to another polymer (Poly(ethylene glycol-ran-propylene glycol)) - this is typical copolymer of ethylene oxide and propylene oxide with disordered structure. So, the properties of such copolymer could be expressed as averaged properties of PEG and PPG polymers without any characteristic features of the structural fragments along the copolymer chain.

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1st Jan, 2014

Ebrahim Jalali Dil

Polytechnique Montréal

The most important difference in my view point is that in the block copolymers, each block (if the length is long enough) keeps its characteristics, so for example in your case, PEO-PPO-PEO, each block has its own Tg. You also should consider that , block copolymers can arrange themselves in different morphologies depending on the block length and block length ratio (they can have droplet-like phase, rod-like phase, sheets or cocontinous structure). On the other hand, in random copolymers, you usually can expect an average properties of both polymer (Not always). For example, it is most probable for a random copolymer to show only one Tg. Yet the properties of a random copolymer depends on its molecular structure. Some random copolymers are in the form of ABABABA while some others may have some sequences of the monomers such as AABABBBAABABBAAAAA.

This discussion stands for the two materials that you mentioned above. So the choice between these materials depends on the application, for example, the block copolymer can be used as emulsifier while the random copolymer cannot .

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1st Jan, 2014

Charles Francis Palmer

Ethox Chemicals, LLC

The EO/PO block copolymers behave in water much differently than do the random ones. The PO blocks have little water solubility and so will move to the oil or solid or air interfaces. This makes them useful surfactants for making emulsions or dispersions. Depending on the block lengths and their orientation EO-PO-EO or PO-EO-PO you get good surfactants for making oil in water or water in oil emulsions. If the EO chain is long enough, you can also get good steric stabilization of particles or oil droplets. These block copolymers are sold in the tens of millions of pounds per year. I don't know of any significant commercial use for the random EO/PO copolymers.

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1st Jan, 2014

Ty Khosravi

Dear all,thank you for your useful explanations.

Can you help by adding an answer?

Answer