| 释义 |
ˈstereoblock Chem.
[ad. It. stereoblocchi (G. Natta et al. 1957, in Chim. e Industr. XXXIX. 276/2): see stereo- and block n.]
A segment of a polymer chain possessing stereoregularity. Also attrib., as stereoblock polymer, a polymer the chains of which contain such segments.
1957Chem. Abstr. LI. 12536 New linear high polymers of α-olefins are described which are distinguished by the presence within the macromol. of chain portions of different steric configurations. Designated ‘stereoblock’ polymers.., these differ from the block copolymers in that the former are obtained by polymerization of a single type of monomer. 1959Gaylord & Mark Linear & Stereoregular Addition Polymers 483 As originally defined by Natta, stereoblock polymers of α-olefins are polymers consisting of macromolecules containing crystallizable segments having isotactic structure and noncrystallizable segments. Actually, these macromolecules may consist either of both isotactic and atactic segments or of adjacent isotactic segments having different steric configuration... In practice, amorphous polymers, considered as atactic, may contain very short stereoblocks. 1979C. H. Bamford in R. N. Haward Developments in Polymerisation II. 253 The ‘hopping’ of a propagating chain from an isotactic to a syndiotactic matrix (or vice versa) could give rise to a stereoblock daughter polymer. 1980Jrnl. Polymer Sci.: Polymer Physics Ed. XVIII. 630 The length and the type of junctions between isotactic stereoblocks affects the crystallization of polypropylene. |