Poly(vinyl cinnamate)
CAS: 9050-06-0
Under UV irradiation, poly(vinyl cinnamate)
(PVCi) films undergo cross-linking due to [2 + 2]
photocycloaddition between cinnamoyl groups.
Consequently, electronic configuration of lateral
polymer groups changes and also leads to the drop
of the refractive index in the visible range.
This mechanism is studied with regards to the
level of the electronic absorption of cinnamate
centered at 278 nm. It acts on refractive index
by shifting the absorption UV band. Most of the
time, this influence vanishes in the near infrared
region (NIR). It is due to antagonist phenomena
acting at the expense of the index lowering.
The causes analysis leads us to optimize the
irradiation spectrum, providing higher index
contrasts between irradiated and nonirradiated
area. We show that strong index changes can be
achieved in PVCi film, up to 2.5 10-2 even in the
NIR, enabling us, for example, to perform optical
photoprinting waveguides for telecommunication
wavelengths (1300-1550 nm).