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INTRODUCTION
Interest has grown in the design and use of polymeric
photoinitjators with one of the main motivating influences being
the desire to reduce the number of migratable low molecular
weight species present in the cured film [1]. Such species are
believed to be responsible for the phenomenon of blooming [2]
ie. loss of glass of the film upon ageing. A further
particularly important aspect is that migratable species pose a
problem for food aging etc, since'they may pass into the
packaged product imparting unwanted smell taint or even adverse
toxicological effects. Another potential advantage of polymeric
photoinitiators has been perceived as their increased efficiency
In absorbing radiation via the antennae effect [1,3,4].
Most of the polymeric initiators developed so far lead to
fragments which are attached to the polymer backbone [5] or if a
fragment is released, it is a highly volatile species and is
therefore probably removed by the heat.available.in the curing
process [6]. An interesting facet of such initiators is the
question as to whether the reactivity of the initiating radical
or that of the propagating radical is modified as a result of
being appended to apolymer chain [3,4]. There is some evidence
that tethering radicals to polymer backbones can in fact reduce
reactivity [7].
We now describe polymeric photoinitiators in which some of the
generated radicals are cleaved fromthe polymer backbone and may
therefore initiate polymerisation in the usual way.
