Sentence:  Related to micelle formation is the technologically important ability of detergent actives to congregate at oil water interfaces in such a manner that the polar ( or ionized ) end of the molecule is directed towards the aqueous phase and the hydrocarbon chain towards the oily <WSD>phase</WSD> . 
Meaning of the word marked with <WSD> tags:  (physical chemistry) a distinct state of matter in a system; matter that is identical in chemical composition and physical state and separated from other material by the phase boundary