Chain Trajectory and Crystallization Mechanism of a Semicrystalline Polymer in Melt- and Solution-Grown Crystals As Studied Using ¹³C–¹³C Double-Quantum NMR

Abstract

The re-entrance sites, successive chain-folding number ⟨n⟩, and chain-folding fraction ⟨F⟩ of the chain-folding (CF) structure of 13C CH3-labeled isotactic poly­(1-butene) (iPB1) with an weight-averaged molecular weight (⟨M w⟩ = 37 K g/mol) in solution- and melt-grown crystals as a function of crystallization temperature (T c) were determined using solid-state (SS) NMR. The solution- and melt-grown crystals possessed adjacent re-entry structures between the right- and left-handed stems along the (100) and (010) planes, which were invariant as a function of T c. The adjacent re-entry structures in the former exhibited long-range order (⟨n⟩ ≥ 8) compared with that in the latter (⟨n⟩ ≥ 1.7–2). These results indicated that the concentration and entanglement of polymers play significant roles in the CF process and structural formation during the initial stage of crystallization, whereas kinetics does not. Transmission electron microscopy (TEM) revealed well-defined hexagonal and circular crystals grown from the solution state at T c = 60 and ∼0 °C, respectively. The morphological and molecular-level structural data demonstrated that kinetics influences the structural formations of polymers differently at different length scales during crystallization. Moreover, SS-NMR, small-angle X-ray scattering (SAXS), and atomic force microscopy (AFM) indicated that the crystallinity (χc) and lamellar thickness (⟨l c⟩) of the melt-grown crystals are highly dependent on T c, whereas in the solution-grown crystals, these parameters are independent of T c. The experimental results and molecular dynamics, as reported in the literature, indicated that both χc and ⟨l c⟩ are primarily determined by the molecular dynamics of the stems after deposition of the chains on the growth front (late process).

Three-Dimensional Conformation of Folded Polymers in Single Crystals

“…Solid-state NMR (SS-NMR) is a sophisticated technique for the structural and dynamic analysis of inorganic materials and organic molecules [15][16][17][18][19][20][21]. Among the various magnetic interactions, dipolar interactions, which are inversely proportional to the third power of the internuclear distance, have been successfully used to determine the local conformation and packing of polymers [15] and peptides [16,17], intermolecular interactions of self-assembly systems [18] and 3D structure of peptides [19] and proteins [20].…”

“…Among the various magnetic interactions, dipolar interactions, which are inversely proportional to the third power of the internuclear distance, have been successfully used to determine the local conformation and packing of polymers [15] and peptides [16,17], intermolecular interactions of self-assembly systems [18] and 3D structure of peptides [19] and proteins [20]. Recently, we proposed a strategy to investigate detailed CF structures in which the adjacent re-entry sites, successive adjacent re-entry number <n>, and adjacent re-entry fraction <F> are obtained from the analysis of 13 C- 13 C double-quantum (DQ) buildup curves [21]. Such data is sensitive to the spatial arrangement of 13 C labels, and detailed information on the chain folding is obtained by comparison with data simulated on the basis of different models.…”

In situ POM and FTIR investigation on quiescent phase transition of polybutene‐1 from form II to form I

“…With folded‐chain cluster as research objects, let us see their stress conditions. Recently, Miyoshi et al found with 13 C‐ 13 C double‐quantum NMR that a chain existed mainly in the form of folded‐chain cluster in PB‐1 crystals . These clusters included two or three stems, which can be regarded as a crystal embryos.…”

“…Recently, Miyoshi et al found with 13 C-13 C doublequantum NMR that a chain existed mainly in the form of foldedchain cluster in PB-1 crystals. [62][63][64] These clusters included two or three stems, [64] which can be regarded as a crystal embryos. These crystal embryos may be in different states due to different stress conditions, as seen in Figure 14.…”

A Review on Polymer Crystallization Theories

“…Moreover, they acquired the morphology and the corresponding diffraction pattern of the single crystals under a transmission electron microscope, both of which confirmed the formation of a folded chain structure. Subsequent computer simulation [20][21][22][23][24][25][26] and experiments [27][28][29][30] also revealed that a single polymer chain would spontaneously crystallize in a folded manner within an appropriate temperature range.…”