WHY DO POLYETHYLENE CRYSTALS HAVE SECTORS

被引:12
作者
DORSET, DL
HANLON, J
MCCONNELL, CH
FRYER, JR
LOTZ, B
WITTMANN, JC
BECKMANN, E
ZEMLIN, F
机构
[1] UNIV GLASGOW,DEPT CHEM,GLASGOW G12 8QQ,SCOTLAND
[2] INST CHARLES SADRON,CTR RECH MACROMOLEC,F-67083 STRASBOURG,FRANCE
[3] MAX PLANCK GESELL,FRITZ HABER INST,ELEKTRONENMIKROSKOPIE ABT,W-1000 BERLIN 33,GERMANY
关键词
electron diffraction; electron microscopy; image analysis; n-paraffins;
D O I
10.1073/pnas.87.5.1696
中图分类号
O [数理科学和化学]; P [天文学、地球科学]; Q [生物科学]; N [自然科学总论];
学科分类号
07 ; 0710 ; 09 ;
摘要
High-resolution (3.7 Å in optical diffraction) electron microscope images have been obtained from a series of n-paraffin monolamellar crystals with chain lengths from n-C36H74 to n-C82H166. The higher molecular weight specimens, which do not undergo chain folding, form sectorized crystals and the molecular packing is found to include alternate bands of untilted and tilted chains along (130). Their widths are consistent with those of Bragg fringe widths in bright-field images obtained at lower magnification. The chain tilt axis is near d110*. Lower molecular weight paraffins form nonsectorized crystals where the chains are generally untilted with occasional small inclinations around nonspecific axes. Surface decoration of the longer alkanes with polyethylene crystallites, first of all, reveals three preferred polyethylene crystal rod orientations ([100] plus two perpendicular to {110}) instead of the two commonly found for the lower alkane. Control studies on solid-solution crystals reveal that the third [100] orientation is a result of slight surface roughness due to unequal chain lengths or surface protrusions of chains; the new decoration is also randomly distributed. For pure n-C60H122 lamellae, however, suggestions of regular bands containing rods along [100], due to surface discontinuities along (130), can also be seen. In contrast with polyethylene, these data suggest that crystal sectorization may be a function of chain-stem packing alone and that chain folds may play merely a secondary role in the polymer - e.g., by directing the collapse of pyramidal crystals on a flat surface.
引用
收藏
页码:1696 / 1700
页数:5
相关论文
共 27 条
[1]   GROWTH FEATURES ON CRYSTALS OF LONG-CHAIN COMPOUNDS .3. [J].
AMELINCKX, S .
ACTA CRYSTALLOGRAPHICA, 1956, 9 (03) :217-224
[2]   SOME NEW HABIT FEATURES IN CRYSTALS OF LONG CHAIN COMPOUNDS .4. FOLD SURFACE GEOMETRY OF MONOLAYER POLYETHYLENE CRYSTALS AND ITS RELEVANCE TO FOLD PACKING AND CRYSTAL GROWTH [J].
BASSETT, DC ;
KELLER, A ;
FRANK, FC .
PHILOSOPHICAL MAGAZINE, 1963, 8 (94) :1753-&
[3]   ON HABITS OF POLYETHYLENE CRYSTALS [J].
BASSETT, DC ;
KELLER, A .
PHILOSOPHICAL MAGAZINE, 1962, 7 (81) :1553-&
[4]   SOME NEW HABIT FEATURES IN CRYSTALS OF LONG CHAIN COMPOUNDS .3. DIRECT OBSERVATIONS ON UNFLATTENED MONOLAYER POLYETHYLENE CRYSTALS [J].
BASSETT, DC ;
FRANK, FC ;
KELLER, A .
PHILOSOPHICAL MAGAZINE, 1963, 8 (94) :1739-&
[5]   SOME NEW HABIT FEATURES IN CRYSTALS OF LONG CHAIN COMPOUNDS .2. POLYMERS [J].
BASSETT, DC ;
KELLER, A .
PHILOSOPHICAL MAGAZINE, 1961, 6 (63) :345-&
[6]   EVIDENCE FOR DISTINCT SECTORS IN POLYMER SINGLE CRYSTALS [J].
BASSETT, DC ;
FRANK, FC ;
KELLER, A .
NATURE, 1959, 184 (4689) :810-811
[7]   CHARACTERIZATION OF STRIATIONS IN POLYETHYLENE SINGLE-CRYSTALS [J].
BOUDET, A .
JOURNAL OF MATERIALS SCIENCE, 1984, 19 (09) :2989-2996
[8]  
CHAMPENEY DC, 1973, FOURIER TRANSFORMS T, P25
[9]   SECTORIZATION OF N-PARAFFIN CRYSTALS [J].
DORSET, DL .
JOURNAL OF MACROMOLECULAR SCIENCE-PHYSICS, 1986, B25 (1-2) :1-20
[10]   POLYMETHYLENE CHAIN PACKING IN EPITAXIALLY CRYSTALLIZED CYCLOALKANES - AN ELECTRON-DIFFRACTION STUDY [J].
DORSET, DL ;
HSU, SL .
POLYMER, 1989, 30 (09) :1596-1602