| DAVID CHELAZZI1,
MATTEO CEPPATELLI1, 2,
MARIO SANTORO1, 3,
ROBERTO BINI1, 2 and
VINCENZO SCHETTINO1, 2
1 Dipartimento di
Chimica dell'Università di Firenze, Via della Lastruccia
3, I-50019 Sesto Fiorentino, Firenze, Italy
2 LENS, European Laboratory for Non-linear
Spectroscopy and INFM, Via Carrara 1, I-50019 Sesto
Fiorentino, Firenze, Italy
3 Present address: Geophysical Laboratory,
Carnegie Institution of Washington DC, USA
Correspondence to:
ROBERTO BINI bini@chim.unifi.it
Nature Materials
AOP Published online: 6 June
2004 | doi:10.1038/nmat1147 |
|
Polymerization processes are probably the most relevant
example of a chemical reaction activated by catalysts or
radical initiators. Among polymers, polyethylene is by
far the most common and largely produced. Here we
present a high-pressure synthesis of high-density
crystalline polyethylene by using only physical tools
such as pressure and light. Low-density polyethylene is
obtained by compressing ethylene at room temperature
above 3 GPa in the ordered crystal phase, and a highly
crystalline polymer is produced in the fluid phase at
pressures lower than 1 GPa by using continuous-wave
laser lines (
460 nm) as an optical catalyst. The photo-activation is
based on a two-photon absorption process to
 *
antibonding states, where the change in molecular
geometry favours the polymeric chain formation. The high
yield and crystallinity of the polymer recovered by the
photoinduced reaction and the simplicity of the
synthesis make this process appealing for large-scale
applications.
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