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单词 stereoblock
释义

stereoblockn.

Etymology: < Italian stereoblocchi (G. Natta et al. 1957, in Chim. e Industr. XXXIX. 276/2): see stereo- comb. form and block n.Previous versions of the OED give the stress as: ˈstereoblock.
Chemistry.
A segment of a polymer chain possessing stereoregularity. Also attributive, as stereoblock polymer, a polymer the chains of which contain such segments.
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stereoblock polymer1957
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stereoblock1957
1957 Chem. Abstr. 51 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.
1959 Gaylord & 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.
1979 C. 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.
1980 Jrnl. Polymer Sci.: Polymer Physics Ed. 18 630 The length and the type of junctions between isotactic stereoblocks affects the crystallization of polypropylene.
This entry has not yet been fully updated (first published 1986; most recently modified version published online June 2019).
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