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 (λ ≤ 460 nm) as an optical catalyst. The photo-activation is based on a twophoton absorption process to π* 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.
High-pressure photodissociation of water as a tool for hydrogen synthesis and fundamental chemistry / M.Ceppatelli; R.Bini; V.Schettino. - In: PROCEEDINGS OF THE NATIONAL ACADEMY OF SCIENCES OF THE UNITED STATES OF AMERICA. - ISSN 0027-8424. - STAMPA. - 106:(2009), pp. 11454-11459. [10.1073/pnas.0901836106]
High-pressure photodissociation of water as a tool for hydrogen synthesis and fundamental chemistry
CEPPATELLI, MATTEO;BINI, ROBERTO;SCHETTINO, VINCENZO
2009
Abstract
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 (λ ≤ 460 nm) as an optical catalyst. The photo-activation is based on a twophoton absorption process to π* 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.File | Dimensione | Formato | |
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