Identification and quantification of the crystalline structures of poly(vinylidene fluoride) sutures by wide-angle X-ray scattering and differential scanning calorimetry

Abstract

The outstanding biocompatibility of the polyvinylidene fluoride (PVDF) monofilament suture together with other desirable characteristics, such as ease of handling and resistance to biodegradation, makes it an attractive alternative monofilament suture material for cardiovascular surgery. However, to achieve a high performance suture, the polymeric raw material must be exposed to different treatments, which lead to different degrees and types of crystallization. Since these crystalline modifications deeply influence the mechanical characteristics and the biostability of the sutures, the authors hereby propose a method of quantifying the different structures of PVDF using wide angle X-ray diffraction (WAXD) and differential scanning calorimetry (DSC). The commercial devices are achieved by coloring and processing the polymeric raw material. The white and unprocessed 4-0 unswaged suture presents 19% of the alpha phase, 38% of the beta structure, and no gamma form. Coloration increases the amount of the beta phase by 5-9% at the expense of the alpha phase. On the other hand, processing the fibers lead to the conversion of some of the amorphous phase to the gamma structure, the importance of which is 6-7%. Finally, tensile measurements performed on the different PVDF fibers clearly proves that their mechanical characteristics depend on the presence of these crystalline forms in the polymeric structure of PVDF.

Surface characteristics and blood compatibility of PVDF/PMMA membranes

“…With exceptional chemical resistance, wonderful thermal stability, biostability, and excellent biocompatibility, PVDF is also employed as soft tissue repair and structure materials [1][2][3][4]. However, PVDF is a hydrophobic polymer without any functional groups to promote cell adhesion on surface.…”

Modification on crystallization of poly(vinylidene fluoride) (PVDF) by solvent extraction of poly(methyl methacrylate) (PMMA) in PVDF/PMMA blends

“…Because of its excellent piezoelectric, chemical and physical properties, poly(vinylidene fluoride) (PVDF) has attracted more and more attention in recent years [1][2][3][4] and has been widely applied in many industrial fields, such as sensor devices [5], battery separators [6][7][8], and biomedicine [9]. According to previous studies, PVDF has five crystal phases, which involve three different chain conformations, namely, β-phase (TTTT), α-and δ-phase (TGTG′), γ-and ε-phase (TTTGTTTG′) [10][11][12].…”

The Synthesis and Crystallization of Poly(vinylidene fluoride) in Supercritical CO2

“…Figure 3 shows the significant amount of α crystal phases of PVDFs by WAXRD [19,21,24], however, it is usually difficult to separate pronounced features resulting from trans sequence in the β or γ crystalline phases by WAXRD [40,41]. Thus, Figure 3 can't be used to compare the amount of different crystalline phases.…”

“…Thus, Figure 3 can't be used to compare the amount of different crystalline phases. Furthermore, the amount of crystalline phases of PVDF was calculated using DSC curve analysis [21]. During the first heating round, a small melting peak of incomplete crystal was observed in the DSC trace, but it disappeared in the second round of the DSC heating process.…”

“…So far, the crystallization of commercial PVDF (not by sc-CO 2 polymerization) under electric fields or high pressure or by heat treatments has been studied [17][18][19][20][21][22][23]. It is found that many factors, such as the temperature, H-H defect, electric fields, pressure, molecular weight and chain end groups, affect the crystalline phases (α, β, and γ phase), phase transition and crystallinity of PVDF [24][25][26].…”