National Textile Center

Year 8 Proposal

Project No.: M98-A16

Competency: Materials

Intelligent, Stimuli-Sensitive Fibers and Fabrics

Project Team:

Leader William K. Walsh Expertise Materials and chemical modification

Email: wwalsh@eng.auburn.edu Phone: 334.844-5452

Name/school/expertise

Members: Gisela Buschle-Diller Auburn Textile chemistry

Aliecia McClain Auburn Organic Synthesis

Moussa Traore Auburn Organic and Textile Chemistry

Sam Hudson NCSU Fiber formation

Objective:

Currently there are no textile materials that regulate their performance in a desirable manner when the surrounding environment changes. Recent progress in stimuli-sensitive polymers (SSP’s) has inspired our idea to create intelligent textiles which self-regulate structure and performance in response to environmental variation. The underlying concept for this research is that, by molecular designs of special SSP’s having appropriate phase change behaviors and by incorporating SSP’s into or on the surface of fibers, we can generate stimuli-sensitive textiles with specific properties (permeation, hydrophilicity, mass and heat transport, physical shape, moisture absorption, light reflectance, etc) that are sensitive to small environmental changes.

The goal of the research is to determine and meet the requirements for SSP textiles and to study the molecular and physicochemical principles of phase changes that control their properties.

Relevance to NTC Mission:

There is an increasing demand for novel functional fibers in multi-billion dollar markets which include sport garments, interior textiles, hygienic textiles, protective clothing, agricultural and geotextiles, and other technical fabrics (sensors, quality control, and communication). There will be intense global competition in this emerging field (they are already being explored in Japan) and it is important that the domestic textile industry be the leader.

Success in this investigation will meet the NTC goal of creating new materials with new functionality that will help the US textile industry grow and lead the world. It will put us at the forefront of this new scientific area and will give the industry the tools it needs to develop products based on it.

State of the Art:

Intelligent, responsive textiles based on SSP’s constitute a new field in the scientific frontier of smart materials. The attractive aspects of SSP’s are their unique capabilities to reversible and sharply change structure and properties in response to relatively small environmental variation. SSP’s have numerous applications (acting as a chemical valve with controlled delivery of functional substances, temperature and moisture regulation, intelligent separation, communication, robotic muscles, sensors, quality control, etc.). Most current research is directed toward syntheses of SSP’s with various types of responsiveness. Mitsubishi Industries, LTD in Japan has developed thermally responsive shape memory fabrics, but other responsive textiles have not made their appearance. In spite of the obvious attractiveness of self-regulating textiles, no systematic research has been conducted in this area. Because requirements for textile SSP’s are so different from those of the non-textile SSP’s,

our research promises to open an entirely new research field in terms of chemical/physical structures, target properties, and the mechanics of the responsive phase change.

Approach:

Specifically, we will generate SSP textiles by extrusion of SSP’s and surface grafting/coating of SSP’s on existing fibers using ionizing and high intensity ultraviolet radiation. With this approach, the SSP will contribute to the self-regulating functions and the fibrous architecture will provide strength, flexibility, and high surface area/mass (which greatly enhances response time). SSP candidates for this approach are polymers that undergo significant phase changes (chain association, chain conformation, and configuration, swelling, aggregation, etc.) and thus change physical and chemical properties in responses to stimuli. Thermally responsive hydrogels, amphiphilic polymers, and shape memory polymers are among these SSP’s. The properties to be studied will include water absorption, heat and mass transfer, physical shape, wettability, permeation, delivery of functional compounds, transmission of light, and stress signals, etc. The chemical and physical structures of SSP’s dominate the phase change mechanism and therefore control the self-regulation of these properties.

Picture not available.

Figure 1. Mechanism of action of stimuli-sensitive polymers

The above diagram illustrates one of the possible basic principles involved. A fiber is coated with an SSP and swollen with water and an active substance. As the environment changes, the SSP collapses dramatically and releases the active substance. At NCSU, the plan is to extrude fibers composed entirely of SSP’s. Many other combinations are possible and our goal is to develop fibrous structures with a number of capabilities.

The key question that need to be addressed are: 1) what type of SSP structure can and should be generated for desirable textile performance; 2) how and why textile-related SSP’s should behave to give the target performance; and 3) what are the mechanisms dominating the structure formation and the specific responsive behaviors.

The primary barriers to this approach are 1) the lack of knowledge about SSP’s for functional textiles and 2) the reactivities of various fibers to attachment of SSP’s.

This Year’s Goal:

Extrusion of fibers formed entirely of SSP’s or with SSP’s as a coating is being explored at NCSU. Sam Hudson plans to work on forming fibers from wet spun, cross-linked polyelectrolyte gels. These should undergo transformations with changes in pH or electrolyte concentration. Fibers will be based on polyacrylic acid, carboxymethyl cellulose, and chitosan. These fibers gives both anionic and cationic structures and a range of chain stiffness. The flexibility of the polymer chain plays a key role in the action of the chemical valve effect. NCSU workers have assembled excellent wet spinning equipment and will cross-link extruded fibers to achieve various degrees of swelling and stiffness.

Workers at Auburn have grafted polyproplylene and nylon fibers with polyacrylic acid and a copolymer of PAA and N-isopropyl acrylamide, respectively, using gamma irradiation and have demonstrated dramatic conformational changes with both temperature and pH. A high intensity UV irradiator has been purchased and Auburn investigators plan to use it to cross-link existing SSP forming polymers on the surface of textile materials and to form SSP’s in situ using combinations of monomers, di-functional oligomers and polymers. Studies of existing non-fibrous SSP’s will be a guide to choosing proper combinations of monomers, oligomers and polymers for UV curing.

Promising fibrous SSP’s from both methods will be studied for their response to various stimuli. Factors to be considered will be structural and conformational changes such as configuration, chain association, ionization, phase changes, degree of swelling, and morphology.

Outreach to Industry:

We have had extensive contact with the following companies, who have expressed interest and willingness to participate: EMS Associates, Technical Development Corporation, Patagonia, Sterling Fibers, and Fusion Systems.

New Resources Required:

No new resources are required. NCSU has excellent wet spinning equipment and Sam Hudson is internationally recognized for his work in extrusion and in chitosan. Auburn has purchased a six-inch UV curing unit from Fusion UV Systems, Inc. with a lamp powered at 300 watts/in and a conveyor system. Many UV curing systems will cure at line speeds of over 100 ft/min with lamps of this wattage. Bill Walsh has many years of experience in radiation grafting and curing, Aliecia McClain has expertise in organic polymer chemistry and polymer characterization, Gisela Buschle-Diller has extensive qualifications in wet processing of textiles. Moussa Traore is an organic chemist with textile wet processing experience.