Epitaxial crystallization of precisely fluorine substituted polyethylene induced by carbon nanotube and reduced graphene oxide

Epitaxial crystallization of precisely bromine-substituted polyethylene induced by carbon nanotubes and graphene

“…Consequently, the thickness of kebab crystals increases with the increasing crystallization temperature: from 6.0 AE 0.6 nm at 40 C to 6.8 AE 0.5 nm at 60 C (Table 1). From the data analysis shown in Table 1, one can draw the conclusion that the crystallization temperature has great inuence on the size and periodicity of the shish-kebab crystals and the most suitable crystallization temperature for PE21Br/SWCNT in p-xylene is 50 C. In contrast to the previous study, it was found that the diameter of the PE21Br kebab is much smaller than that of HDPE (50-80 nm) 30 and PE21F (54-65 nm) (van der Waals radius of F is 1.52Å) 39 and also smaller than that of PE21Cl (26.2 AE 1.0 nm) (the van der Waals radius of Cl (1.75Å) is smaller than that of Br (1.85Å)). 40 The diameter of the kebab decreases with the increasing volume of the substituent, indicating that the substituent, as a defect of the chain, greatly inuences the lateral growth of the crystal lamellae.…”

“…A larger substituent also causes greater disturbance of the crystallization of PE, which is evidenced by the fact that the thickness of PE21Br kebabs is smaller than that of PE21F formed at the same undercooling degree (10 C). 39 However, the thickness of kebabs does not consistently decrease, as anticipated, with the increasing volume of the substituents. Unexpectedly, the thickness of PE21Br kebabs (6.8 AE 0.5 nm) is almost the same as that of PE21Cl (6.4 AE 0.5 nm).…”

“…It is evident that the average diameter of the PE21Br kebab crystals rst increases, then decreases with the increase in crystallization temperature, and the kebab crystal with the largest diameter forms at 50 C. This behavior is consistent with that of PE21F and PE21Cl crystals reported in Scheme 2 Fabrication process of PE21Br/nanofiller composites. our previous studies, 39,40 which can be attributed to the competition of nucleation and crystal growth on the CNT. Unlike the changes in the diameters, the kebab interval monotonically increases with the increase in the crystallization temperature (Table 1) because the crystal nucleus becomes less and less stable with the decrease in the degree of undercooling.…”

“…Simulation studies again exhibited that graphene has much stronger interactions with polymers and thus displays more important inuence on the structures and properties of polymers than CNT as well as other nanoparticles. 37,38 In our previous studies, 39,40 the precise acyclic diene metathesis polymerization (ADMET) polyethylenes with halogen atoms (F and Cl) placed on each 21st backbone carbon (PE21F and PE21Cl, respectively) were chosen to investigate the effects of structural change upon the epitaxial crystallization of the substituted-polymers. The results showed that CNT had almost no effect on the crystal structure of both PE21F and PE21Cl, whereas reduced graphene oxide (RGO) induced the structural transformation of PE21Cl from the triclinic to orthorhombic form and generated extraordinarily high melting temperatures.…”

“…The results showed that CNT had almost no effect on the crystal structure of both PE21F and PE21Cl, whereas reduced graphene oxide (RGO) induced the structural transformation of PE21Cl from the triclinic to orthorhombic form and generated extraordinarily high melting temperatures. 39,40 The two distinctively different crystal structures resulting from variant surfaces not only suggest that precisely substituted polyethylenes are an ideal model to study the inuence of substituents on epitaxial crystallization, but also indicate the different inducing abilities of CNT and graphene.…”