麻豆淫院

A team of researchers affiliated with multiple institutions in China and one in the Netherlands has found a new way to view the creation process of polyethylene. In their paper published in the journal Science, the group describes their process and what it revealed. Joost Wintterlin, with Ludwig Maximilians-Universit盲t M眉nchen, provides a Perspective piece in the same journal issue describing the work done by the team.

Polyethylene is a common and popular type of plastic. It currently makes up approximately one-third of all plastics produced. Despite its widespread use and long history of study, scientists have not really understood what happens when such plastics are made because methods to view the process are quite limited. All of them are made using catalysts that assist in linking ethylene molecules together. In this new effort, the researchers have developed a way to watch the entire process unfold using scanning tunneling microscopy (STM).

The researchers started by using a thin-film iron carbide, with staggered rows of iron trimmers to serve as connection sites, laid flat on a crystal base. Under this arrangement, polyethylene forms on the surface of the catalyst when ethylene is applied. To capture the action, the whole setup was placed in a chilled vacuum case under an STM. By manipulating the temperature and dosing of the iron carbide, the researchers were able to create a stop-motion video that showed in slow motion what was happening as the polyethylene was created.

The researchers were able to see the monomers being absorbed and the formation of intermediate polymer chains as they began to grow; the chains were attached to the active centers while the other ends remained mobile. The researchers also note that their video shows that the Cossee鈥揂rlman hypothesis鈥攑ublished in 1964, shortly after polyethylene was discovered鈥攚as correct. Researchers back then proposed that polymer chains were propagated due to insertion of monomer units into carbon-metal bonds. Wintterlin suggests that the work could have an important impact on industrial efforts involved in producing polyethylene because it opens the door to manipulating the average length of the molecules produced, which could lead to the development of new products.

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