English to Portuguese Science Chemistry; Chem Sci/Eng Polymers

A "3-block structure" is a polyether polyol in which the starter compound (e.g., glycerol) is first lengthened with exclusively propylene oxide (PO) so that a pure PO block is formed, then reacted with a mixture of ethylene oxide (EO) and propylene oxide (PO) to form a mixed block with random distribution of the EO and PO units (such a mixed block is also called a "random EO/PO mixed block") and then reacted with ethylene oxide exclusively in a third step to obtain a pure EO block at the chain end. The third step is also referred to as "EO cap" in the following.