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US-12625073-B2 - Method for characterizing melting transition and crystallization in a semicrystalline polymer

US12625073B2US 12625073 B2US12625073 B2US 12625073B2US-12625073-B2

Abstract

A method for characterizing a melting transition in a semicrystalline polymer is disclosed. The method includes incorporating a fluorophore into the semicrystalline polymer, changing a temperature of the semicrystalline polymer to vary across a range of temperatures including a plurality of temperatures, and capturing an emission spectrum of the incorporated fluorophore at each temperature of the plurality of temperatures. The method also includes integrating each emission spectrum to determine a temperature-dependent integrated fluorescence intensity for the semicrystalline polymer, numerically differentiating the temperature-dependent integrated fluorescence intensity, and characterizing the melting transition of the semicrystalline polymer by identifying a stepwise change in value of the differentiated intensity. The semicrystalline polymer may be a thermoplastic. Incorporating the fluorophore into the semicrystalline polymer may include physically doping the semicrystalline polymer with the fluorophore or covalently labeling the semicrystalline polymer with the fluorophore.

Inventors

  • Kailong Jin
  • Richard Nile

Assignees

  • Kailong Jin
  • Richard Nile

Dates

Publication Date
20260512
Application Date
20221025

Claims (20)

  1. 1 . A method for characterizing a melting transition in a semicrystalline polymer, comprising: incorporating a fluorophore into the semicrystalline polymer; changing a temperature of the semicrystalline polymer to vary across a range of temperatures comprising a plurality of temperatures; capturing an emission spectrum of the incorporated fluorophore at each temperature of the plurality of temperatures; integrating each emission spectrum to determine a temperature-dependent integrated fluorescence intensity for the semicrystalline polymer; numerically differentiating the temperature-dependent integrated fluorescence intensity; and characterizing the melting transition of the semicrystalline polymer by identifying a stepwise change in value of the differentiated intensity.
  2. 2 . The method of claim 1 , wherein the melting transition is melt crystallization.
  3. 3 . The method of claim 2 , wherein the melt crystallization is observed in a temperature range of 195° C. to 60° C. or any subset range within the 195° C. and 60° C. range.
  4. 4 . The method of claim 1 , wherein the semicrystalline polymer is a thermoplastic.
  5. 5 . The method of claim 1 , wherein the semicrystalline polymer comprises at least one of polyethylene, polypropylene, poly(L-lactic acid) (PLLA), poly(caprolactone) (PCL), and poly(ethylene oxide) (PEO).
  6. 6 . The method of claim 1 , wherein incorporating the fluorophore into the semicrystalline polymer comprises physically doping the semicrystalline polymer with the fluorophore.
  7. 7 . The method of claim 1 , wherein incorporating the fluorophore into the semicrystalline polymer comprises covalently labeling the semicrystalline polymer with the fluorophore.
  8. 8 . The method of claim 1 , wherein the fluorophore comprises 1,2-bis(2,4-dihydrobenzylidene) hydrazine.
  9. 9 . The method of claim 1 , wherein the capturing an emission spectrum of the incorporated fluorophore comprises placing the semicrystalline polymer with incorporated fluorophore on a quartz slide.
  10. 10 . The method of claim 9 , wherein the semicrystalline polymer with incorporated fluorophore is cast on the quartz slide from a solution comprising the semicrystalline polymer with incorporated fluorophore.
  11. 11 . A method of characterizing a melting transition of a semicrystalline polymer having an incorporated fluorophore, the method comprising: changing a temperature of the semicrystalline polymer to vary across a range of temperatures comprising a plurality of temperatures; capturing an emission spectrum of the incorporated fluorophore at each temperature of the plurality of temperatures; integrating each emission spectrum to determine a temperature-dependent integrated fluorescence intensity for the semicrystalline polymer; numerically differentiating the temperature-dependent integrated fluorescence intensity; and characterizing the melting transition of the semicrystalline polymer by identifying a stepwise change in value of the differentiated intensity.
  12. 12 . The method of claim 11 , wherein the melting transition is melt crystallization.
  13. 13 . The method of claim 12 , wherein the melt crystallization is observed in a temperature range of 195° C. to 60° C. or any subset range within the 195° C. and 60° C. range.
  14. 14 . The method of claim 11 , wherein the semicrystalline polymer is a thermoplastic.
  15. 15 . The method of claim 11 , wherein the semicrystalline polymer comprises at least one of polyethylene, polypropylene, poly(L-lactic acid) (PLLA), poly(caprolactone) (PCL), and poly(ethylene oxide) (PEO).
  16. 16 . The method of claim 11 , wherein incorporating the fluorophore into the semicrystalline polymer comprises physically doping the semicrystalline polymer with the fluorophore.
  17. 17 . The method of claim 11 , wherein incorporating the fluorophore into the semicrystalline polymer comprises covalently labeling the semicrystalline polymer with the fluorophore.
  18. 18 . The method of claim 11 , wherein the fluorophore comprises 1,2-bis(2,4-dihydrobenzylidene) hydrazine.
  19. 19 . The method of claim 11 , wherein the capturing an emission spectrum of the incorporated fluorophore comprises placing the semicrystalline polymer with incorporated fluorophore on a quartz slide.
  20. 20 . The method of claim 19 , wherein the semicrystalline polymer with incorporated fluorophore is cast on the quartz slide from a solution comprising the semicrystalline polymer with incorporated fluorophore.

Description

CROSS-REFERENCE TO RELATED APPLICATIONS This application claims the benefit of U.S. Provisional Application No. 63/279,387, entitled “Method for Characterizing a Melting Transition in a Semicrystalline Polymer” which was filed Nov. 15, 2021, the entire disclosure of which is hereby incorporated herein by this reference. TECHNICAL FIELD Embodiments of the present disclosure relate to the field of characterizing melting transitions and crystallization in semicrystalline polymers. BACKGROUND The melting point (Tm) is an important physical parameter that dictates the thermal, mechanical, and transport properties of a given semicrystalline polymer, such as a semicrystalline thermoplastic. Below Tm the material is a solid with robust mechanical performance, while above Tm the material is a liquid that is easier to process. Thus, the melting point Tm sets the upper service temperature for semicrystalline thermoplastics, which plays a similar role as the glass transition temperature, Tg, in setting the boundary between solid state application and liquid state processing for amorphous thermoplastics (e.g., polystyrene, poly(methyl methacrylate), etc.). Because perfectly crystalline polymers are rare in real world applications and semicrystalline polymers usually contain crystallites of different sizes, Tm more often represents a melting transition range where large segments of the polymer chain start to move after melting. The ability to precisely determine and thereby engineer Tm is key to the design and application of semicrystalline thermoplastics. Various characterization methods have been employed for probing melting transitions of semicrystalline thermoplastics. These conventional methods can be categorized into three major groups: First, techniques that can observe a thermal and/or mechanical property change around Tm, e.g., differential scanning calorimetry, ellipsometry/spectral reflectance, and shear modulus force microscopy. These techniques can measure Tm by monitoring temperature-dependent heat capacity, thermal expansivity, and modulus, respectively. Second, techniques that can probe morphological or structural change near Tm, e.g., optical microscopy/atomic force microscopy, and X-ray based methods (e.g., X-ray diffraction, grazing-incidence wide-angle X-ray scattering, small angle X-ray scattering, etc.) can measure Tm by monitoring temperature-dependent morphology and microstructure, respectively. Third, techniques that can observe a change in a molecular property (e.g., chain conformation) near Tm, e.g., Raman spectroscopy, Fourier-transform infrared spectroscopy (FTIR), solid-state NMR, etc.). These techniques can measure Tm by monitoring temperature-dependent absorption bands that are indicative of molecular motions and thus chain conformations. Although these conventional methods for characterization have been well developed, they each suffer from various limitations. For example, X-ray based techniques require exposure to X-ray beams which might be detrimental to some soft polymeric materials. Additionally, most of these methods are only able to measure spatially averaged properties throughout a bulk sample or a film cross section. They are not well adapted for characterizing melting transitions in more complicated polymer systems, such as multilayer films, blends, and composites. SUMMARY In some aspects, the disclosure concerns methods for characterizing a melting transition in a semicrystalline polymer, comprising: incorporating a fluorophore into the semicrystalline polymer; changing a temperature of the semicrystalline polymer to vary across a range of temperatures comprising a plurality of temperatures; capturing an emission spectrum of the incorporated fluorophore at each temperature of the plurality of temperatures; integrating each emission spectrum to determine a temperature-dependent integrated fluorescence intensity for the semicrystalline polymer; numerically differentiating the temperature-dependent integrated fluorescence intensity; and characterizing the melting transition of the semicrystalline polymer by identifying a stepwise change in value of the differentiated intensity. In some embodiments, the melting transition is melt crystallization. In certain embodiments, the semicrystalline polymer is a thermoplastic. Some semicrystalline polymer comprise at least one of polyethylene, polypropylene, poly(L-lactic acid) (PLLA), poly(caprolactone) (PCL), and poly(ethylene oxide) (PEO). In certain embodiments, incorporating the fluorophore into the semicrystalline polymer comprises physically doping the semicrystalline polymer with the fluorophore. In some embodiments, incorporating the fluorophore into the semicrystalline polymer comprises covalently labeling the semicrystalline polymer with the fluorophore. Some fluorophores comprise 1,2-bis(2,4-dihydrobenzylidene) hydrazine. In some embodiments, capturing an emission spectrum of the incorporated fluorophore comprises placing the sem