Polyalkylene oxide block co-polymers

These materials were introduced by Wyandotte Chemicals Corp and are made by the sequential addition of propylene oxide and ethylene oxide to a low molecular weight reactive hydrogen compound [31]. The polypropylene oxide mid-block is water insoluble and acts as the hydrophobic part of the molecule in the same way as fatty alcohol in conventional ethoxylates. The addition of ethylene oxide to polypropylene oxide mid-block gives water soluble polyols having surface-active properties and the structure  

The prefixes L, P and F represent the physical forms of the products as liquid, paste and flake respectively. 

Manufacture of the polyols is usually carried out in the same reactors as for ethoxylates. The first step is to dissolve sodium hydroxide in propylene glycol and warm to 120°C. The required amount is charged to the reactor, dehydrated and padded with nitrogen. Once this is achieved propylene oxide is added as fast as it will react, maintaining the temperature at 120°C until the required molecular weight is reached. Then ethylene oxide is added at a rate, which maintains the temperature at 120°C. When all the ethylene oxide is added, the 

A further extension to the range is the Pluronic R surfactants in which the hydrophobic and hydrophilic blocks are reversed to give the structure below  

The process is the same as for the normal block co-polymers the hydrophilic block is first made by adding ethylene oxide to ethylene glycol in the normal conditions to produce a sufficiently long chain molecule which is then capped with propylene oxide to produce the hydrophobic blocks. A similar but less extensive series is available offering an even broader selection of surfactant properties from this type of chemistry. 

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