Reversible swelling and collapsing the latent pores of natural fiber welded biopolymer by way of solvent treatment to regenerate mesoporous or nonporous biopolymeric structures

Abstract

A method of reversible swelling and collapsing of the latent pores of natural fiber welded biopolymer by way of sequential solvent treatment to i) regenerate mesoporous biopolymeric structures, comprising the steps of providing a nonporous natural fiber welded biopolymer composite, submerging the nonporous composite in polar solvent, exchanging submersion solvents, typically starting from a solvent of polar identity and ending with a solvent of nonpolar identity, then removing the solvent; and ii) regenerate nonporous biopolymeric structures, comprising the steps of providing a mesoporous natural fiber welded biopolymer composite, submerging the mesoporous composite in polar solvent, then removing the solvent. A mesoporous biopolymeric structure wherein the NFW nonporous composite expresses a BET surface area change of <5 m2 g−1 to >40 m2 g−1. A nonporous biopolymeric structure wherein the NFW mesoporous composite expresses a BET surface area change of >40 m2 g−1 to <5 m2 g−1.

Description

REFERENCE TO RELATED APPLICATION

This application is a non-provisional of, and claims priority to and the benefits of, U.S. Provisional Patent Application No. 63/537,603 filed on Sep. 11, 2023, the entirety of which is herein incorporated by reference.

BACKGROUND

This disclosure concerns reversible swelling and collapsing the latent pores of natural fiber welded biopolymer by way of solvent treatment to regenerate mesoporous or nonporous biopolymeric structures.

A novel product is described herein concerning mesoporous biopolymeric structures.

This disclosure pertains to (1) procedures for exfoliating, swelling, or otherwise opening, and providing access to, the intrinsic pores created during fiber welding processes and imparted upon biopolymers and their composites, (2) the application and expansion of the “gamut of solvents” as a treatment to access these pores, and (3) the storage, recycling, upcycling, and regeneration of commercial fiber welded materials from nonporous to mesoporous or mesoporous to nonporous by the means designated herein.

This includes the treatment and care for products, produced using fiber welding techniques, which are ameliorated or otherwise maintained by subjecting them to a solvent sequence or “gamut of solvents” to expose or improve their functionality.

The fiber welding process, designated Natural Fiber Welding (NFW) as a commercial process, applies a welding solvent (i.e., typically ionic liquid, or IL) to partially solvate and disrupt the intrinsic hydrogen bonding present in the outer layers of biopolymer materials. When used on adjacent threads, this process creates a composite of welded and interlocking, but non-derivatized, cloth.

Rinsing fiber welded composites with water will remove the ionic liquid, though drying from this hydrated state results in a nonporous material.

The emergence of mesoporosity was demonstrated by drying instead from nonpolar solvents, resulting in xerogels. Appropriate conditions for this transition can be achieved by solvent exchange from the welding solution (i.e., ionic liquid) to water and then to increasingly nonpolar solvents like cyclohexane, with surface areas of around 200 m² g⁻¹ attainable within welded cotton thread. While the majority of this surface area derives from an amorphous layer of cellulose (and is thus not present in non-welded or otherwise neat biopolymer thread), the composite retains robust physical properties due to the presence of internal and unmodified crystalline cellulose I.

Indeed, the combination of accessible mesoporous cellulose and intrinsic structural robustness makes these composites desirable; by embedding nanomaterials or biomolecules within the mesoporous layer, functional composites for a variety of applications (e.g., catalysis, storage, separations) can be created.

Unfortunately, composites that were rendered nonporous, either by drying from water post-weld or by exposure of the xerogel to water (or a sufficiently humid environment) and subsequent drying, are not currently considered for these applications without further modification (e.g., via addition of dissolved extraneous biopolymer to the fabric surface).

Herein, we demonstrate a solution to these long-standing problems.

We demonstrate a procedure for converting nonporous fiber welded biopolymers into mesoporous xerogel composites.

The fiber welding process is shown to establish an intrinsic latent porous network which is accessible as a xerogel when drying from nonpolar solvents. We exploit this property by rinsing nonporous or low-porosity fiber welded biopolymer materials with water, then performing a solvent exchange to cyclohexane using the “gamut of solvents” as described below. Removing solvent from this state, even when the starting material was originally observed as nonporous, results in a porous network and creates a useable xerogel. Commercially, this process allows for long-term storage and regeneration of fiber welded materials that were previously thought to be at end-of-life. Additionally, we can convert a mesoporous fiber welded composite to a nonporous fiber welded composite by rinsing the mesoporous composite with a polar solvent and then removing the solvent.

SUMMARY OF DISCLOSURE

Description

This disclosure concerns reversible swelling and collapsing the latent pores of natural fiber welded biopolymer by way of solvent treatment to regenerate mesoporous or nonporous biopolymeric structures.

A novel product is described herein concerning mesoporous and nonporous biopolymeric structures.

DESCRIPTION OF THE DRAWINGS

The following description and drawings set forth certain illustrative implementations of the disclosure in detail, which are indicative of several exemplary ways in which the various principles of the disclosure may be carried out. The illustrated examples, however, are not exhaustive of the many possible embodiments of the disclosure. Other objects, advantages, and novel features of the disclosure will be set forth in the following detailed description when considered in conjunction with the drawings.

FIG. 1 illustrates a bar chart comparing the BET surface areas of fiber welded cotton threads when using various designated starting solvents and carrying through the gamut of solvents. Note that water, methanol (MeOH), and ethanol (EtOH) were exchanged for isopropanol (IPA), 2-butanone (2B), and cyclohexane (CH) whereas all others were exchanged for 2B-CH). FIG. 1 illustrates pore size distributions and average pore diameters for regenerations using MeOH, dimethyl sulfoxide (DMSO), or water (H₂O) as the starting solvent. FIG. 1 also illustrates the isothermal N₂ (for MeOH, DMSO, and H₂O starting solvents) or Kr physisorption profiles for all BET analyses.

DETAILED DESCRIPTION OF THE INVENTION

This disclosure teaches methods and devices for reversible swelling and collapsing the latent pores of natural fiber welded biopolymer by way of solvent treatment to regenerate mesoporous or nonporous biopolymeric structures.

A novel product is described herein concerning mesoporous biopolymeric structures.

Herein, we demonstrate a solution to these long-standing problems.

We demonstrate a procedure for converting nonporous fiber welded biopolymers into mesoporous xerogel composites.

The fiber welding process is shown to establish an intrinsic latent porous network which is accessible as a xerogel when drying from nonpolar solvents. We exploit this property by rinsing nonporous or low-porosity fiber welded biopolymer materials with water, then performing a solvent exchange to cyclohexane using the “gamut of solvents” as described below.

Removing solvent from this state, even when the starting material was originally observed as nonporous, results in a porous network and creates a useable xerogel.

Similarly, a mesoporous fiber welded composite can be treated with a polar solvent, then the solvent removed to result in a nonporous material.

Commercially, this process allows for long-term storage and regeneration of fiber welded materials that were previously thought to be at end-of-life, thus solving long-standing problems.

Regeneration of Nonporous Cellulosic Material

Example 1

Any fiber welded biopolymer will benefit from this technique.

For cellulosic materials derived from cotton, fiber welding was performed using 1-ethyl-3-methylimidazolium acetate (EMImAc) at 60° C. for 60 min. The weld time and temperature can be varied to increase or decrease the thickness of the amorphous layer. Initial rinses with water to remove the EMImAc, and subsequent drying in a 60° C. oven, creates a nonporous composite with a Brunauer-Emmett-Teller (BET) surface area of ca. 0.01 m² g⁻¹.

This is the starting material for demonstrating the regeneration technique.

Example 2

A 50 mg cutting of this composite was submerged in 50 mL of water for 24 h. Water is a known plasticizer for cellulose, and there is swelling of the porous structure. The hydrated material was then transferred, sequentially, to 50 mL of IPA, 50 mL of 2B, and 50 mL of CH, with residence times of 24 h per solvent (i.e., the gamut of solvents: H₂O-IPA-2B-CH).

Upon drying from CH, the composite expresses a much higher BET surface area of ca. 110 m² g⁻¹, a remarkable increase of over four orders of magnitude.

To reiterate, this process successfully converts a nonporous piece of fiber welded cloth into a mesoporous xerogel, something which has not been demonstrated to date.

Example 3

To expand this process and probe solvent interactions, the starting solvent was changed to MeOH, EtOH, acetone (C₃H₆O), acetonitrile (ACN), chloroform (CHCl₃), or DMSO. Notably, we avoid regression to more interacting solvents (in this case, stronger hydrogen bonding solvents) by modifying the gamut for non-alcohols to just include the starting solvent, 2B, and CH (e.g., MeOH-IPA-2B-CH versus ACN-2B-CH). Of these, the only starting solvent to achieve a surface area comparable to water was dimethyl sulfoxide (107 m² g⁻¹), with MeOH achieving only 42 m² g⁻¹ and all others achieving less than 1 m² g⁻¹. We demonstrated a correlation between ability to accept hydrogen bonds and swelling capability. Other solvent properties at play may include solvent molecule volume, polarizability, and dielectric constant.

Example 4

In addition to the above, a piece of mesoporous cotton xerogel was exposed to water and dried, resulting in a nonporous material. Subsequent treatment as per the above method successfully regenerated the material to a xerogel, indicating reversibility.

Example 5

Further, an aged piece of nonporous fiber welded lignocellulose (i.e., linen thread) was also successfully converted into a xerogel using the gamut of solvents technique, providing for storage and subsequent regeneration of nonporous products into xerogels at will.

The gamut of solvents treatment is not necessarily limited to the water-IPA-2B-CH sequence, but includes any other starting, intermediate, and finishing solvents and sequences thereof.

The gamut of solvents concept, as used to regenerate fiber welded materials, has also been proven effective with (but is not limited to) DMSO and MeOH.

Finishing solvents can provide tunability in the overall BET surface area by controllably closing pores.

Intermediate solvents can vary based on the two terminal solvents and primarily exist to bridge the polarity gap between the starting and finishing solvent. The gamut of solvents may or may not include intermediate solvents.

The application of the gamut of solvents to fiber welded biopolymer composite does not require the composite to be nonporous, and will regenerate a lower surface area xerogel to a higher surface area xerogel.

Advantages and New Features

• • 1) Our disclosure demonstrates the capability to regenerate and recycle/upcycle nonporous fiber welded biopolymer composites into aerogels/xerogels and vice versa.
  • 2) This discloses that a gamut of solvents is an efficient and adaptable method for accessing pores intrinsic to, but not realized within, nonporous fiber welded biopolymer composites.
  • 3) Our disclosure enables product storage and regeneration for nonporous fiber welded materials, including treatment and care instructions for commercialized products.

The above examples are merely illustrative of several possible embodiments of various aspects of the present disclosure, wherein equivalent alterations and/or modifications will occur to others skilled in the art upon reading and understanding this specification and the annexed drawings. In addition, although a particular feature of the disclosure may have been illustrated and/or described with respect to only one of several implementations, such feature may be combined with one or more other features of the other implementations as may be desired and advantageous for any given or particular application. Also, to the extent that the terms “including”, “includes”, “having”, “has”, “with”, or variants thereof are used in the detailed description and/or in the claims, such terms are intended to be inclusive in a manner similar to the term “comprising”.

Claims

1. A method of reversible swelling and collapsing of the latent pores of natural fiber welded biopolymer by way of sequential solvent treatment to regenerate mesoporous biopolymeric structures from nonporous or low porosity fiber welded materials, comprising the steps of:

providing a nonporous or low porosity natural fiber welded biocomposite;

submerging the nonporous or low porosity natural fiber welded biocomposite in a polar solvent having a dielectric constant ≥20; and

forming a mesoporous biopolymer composite.

2. The method of reversible swelling and collapsing of the latent pores of natural fiber welded biopolymer by way of sequential solvent treatment to regenerate mesoporous biopolymeric structures from nonporous or low porosity fiber welded materials of claim 1 further comprising the step of:

exchanging the polar solvent starting from a solvent of polar identity and ending with a solvent of nonpolar identity having a dielectric constant <5.

3. The method of reversible swelling and collapsing of the latent pores of natural fiber welded biopolymer by way of sequential solvent treatment to regenerate mesoporous biopolymeric structures of claim 2 further comprising the step of:

removing the nonpolar solvent from the mesoporous biopolymer composite.

4. The method of reversible swelling and collapsing of the latent pores of natural fiber welded biopolymer by way of sequential solvent treatment to regenerate mesoporous biopolymeric structures of claim 3 wherein

the nonporous or low porosity natural fiber welded biocomposite expresses a Brunauer-Emmett-Teller (BET) surface area of <5 m2 g−1 prior to the step of submerging the nonporous or low porosity natural fiber welded biocomposite in polar solvent and expresses a BET surface area of >40 m2 g−1 after the step of removing the nonpolar solvent from the mesoporous biopolymer composite.

5. A method of reversible swelling and collapsing of the latent pores of natural fiber welded biopolymer by way of polar solvent treatment to regenerate nonporous biopolymeric structures from a higher surface area fiber welded material, comprising the steps of:

providing a natural fiber welded mesoporous composite;

submerging the mesoporous composite in a polar solvent;

forming a nonporous biopolymer composite; and

removing the polar solvent from the nonporous biopolymer composite.

6. The method of reversible swelling and collapsing of the latent pores of natural fiber welded biopolymer by way of polar solvent treatment to regenerate nonporous biopolymeric structures of claim 5 wherein

the natural fiber welded mesoporous composite expresses a BET surface area of >40 m2 g−1 prior to the step of submerging the mesoporous composite in polar solvent and expresses a BET surface area of <5 m2 g−1 after the step of removing the polar solvent from the nonporous biopolymer composite.

7. A mesoporous biopolymeric structure made from the steps of:

providing a natural fiber welded nonporous composite;

submerging the natural fiber welded nonporous composite in a polar solvent;

forming a mesoporous biopolymeric structure; and

exchanging the solvent, starting from a solvent of polar identity and ending with a solvent of nonpolar identity.

8. The mesoporous biopolymeric structure of claim 7 further comprising the step of:

removing the nonpolar solvent from the mesoporous biopolymeric structure.

9. The mesoporous biopolymeric structure of claim 8 wherein

the natural fiber welded nonporous composite expresses a BET surface area of <5 m2 g−1 prior to the step of submerging the natural fiber welded nanoporous composite in polar solvent and expresses a BET surface area of >40 m2 g−1 after the step of removing the solvent from the mesoporous biopolymeric structure.

10. A nonporous biopolymeric structure made from the steps of:

providing a natural fiber welded mesoporous composite;

submerging the natural fiber welded mesoporous composite in a polar solvent;

forming a nonporous biopolymeric structure; and

removing the polar solvent from the nonporous biopolymeric structure.

11. The nonporous biopolymeric structure of claim 10 wherein

the natural fiber welded mesoporous composite expresses a BET surface area of >40 m2 g−1 prior to the step of submerging the natural fiber welded mesoporous composite in polar solvent and expresses a BET surface area of <5 m2 g−1 after the step of removing the polar solvent from the nonporous biopolymeric composite.