We must first note that the postmodern era outlined here saw the publication of many works of literature and film that were not postmodern in style, intent or theme. Romanticism, modernism, and many other literary movements are still at work even today. Many works simply do not adhere to tenets of postmodernism in this era and so should not be categorized as such.
Looking at works that can be classified as postmodern between 1970 and 2000, we see love treated as 1) a facet of identity and 2) as a projection and 3) as a psychological and cultural product. At postmodernism challenges the potential for permanence (intellectual and/or ideological), love becomes "transitional" as the individual experiencing it becomes a "text".
The consequence of this position is that there can be no final meaning for any text, for as Derrida himself says, “texts are not to be read according to [any method] which would seek out a finished signified beneath a textual surface. Reading is transformational.”
The work of Ronald Sukenick looks at love as a temporary means by which a person might establish a (potentially) positive view of self. In his work the moral bounds that traditionally define relationships are often broken - as are his narratives - by interruption, by "play", and by replacement. Thus love becomes an expression of transience and of the transcience of personal identity.
The work of Don DeLillo, often identified as postmodern, posits love as a dependency and as a bulwark against the uncertainty of postmodernism. This concept is particularly clear in White Noise.
This is not to say that postmodern writers present love as insincere. Kurt Vonnegut retains the simplicity and sentimentality of love in his work, for the most part, and tends to raise honest human emotions to a place of honor and value against a background of mechanized and technology-hypnotized contemporary culture.