Various non-limiting embodiments disclosed herein relate generally to
photochromic compounds, which may be thermally reversible or
non-thermally reversible, and articles made therefrom. Other non-limiting
embodiments relate to photochromic-dichroic compounds, which may be
thermally reversible or non-thermally reversible, and articles made
therefrom. For example, one non-limiting embodiment provides a thermally
reversible, photochromic compound adapted to have at least a first state
and a second state, wherein the thermally reversible, photochromic
compound has an average absorption ratio greater than 2.3 in at least one
state as determined according to CELL METHOD. Another non-limiting
embodiment provides a photochromic compound comprising: (a) at least one
photochromic group chosen from a pyran, an oxazine, and a fulgide; and
(b) at least one lengthening agent L attached to the at least one
photochromic group and represented by the formula
--[S.sub.1].sub.c-[Q.sub.1-[S.sub.2].sub.d].sub.d'-[Q.sub.2-[S.sub.3].sub-
.e].sub.e'-[Q.sub.3-[S.sub.4].sub.f].sub.f'--S.sub.5--P, which is
described herein.