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Polymer Interfaces


Molecular Structures of Buried Interfaces in Polymer Thin Films

Multilayer polymer films are extensively used for the transport and storage of goods in many industries, offering a reliable, sanitary, and inexpensive solution to meet the demands of increasingly complex applications and environments. Each film contains layers with different polarity; therefore it is important to introduce reactive functionalities to nonpolar layers so that they can be well adhered to polar layers.

We are using SFG to study interfacial chemical reactions between different layers in situ nondestructively. Both model systems with spin coated films and commercial casting films and blown films are investigated.

We have successfully elucidated chemical reaction mechanisms at buried interfaces in multilayer polymer films, followed reaction kinetics, and deduced interfacial activation energy. We continue to study interfacial chemical reactions of new polymer films.

We are also studying interfacial interactions between various coatings and polymer films to understand molecular mechanisms of release coating tapes.


Buried Interfaces of Adhesion Promoter (on Metal) and Sealant

Sealants are often designed to encapsulate substrates (e.g., metals) and protect them from corrosion or other exposure. However, many times sealants do not strongly adhere to the substrates. To improve the adhesion and lifespan of sealants, it is common to pre-coat substrates with adhesion promoters before applying sealants.

We are probing the buried interface of adhesion promoter and sealant to understand the molecular interactions. We also monitored the interfacial molecular changes over time in different environments to elucidate the change in adhesion strengths.

This research provides important fundamental knowledge on improving sealant applications for airplanes and automobiles.


Silicone Adhesion Mechanisms

Silicone adhesives are widely used in many important industrial and other applications due to their excellent chemical stability, superb high-temperature resistance, and outstanding mechanical properties. They could be classified based on their formulations with one relying on room temperature vulcanization (RTV) products and the other relying on high temperature vulcanization (HTV) products.

In silicone adhesive formulation, adhesion promoters play important roles in ensuring strong adhesion to various substrates. Extensive research has been performed to study silicone adhesives; however, there is little information about molecular interfacial structures of these adhesives. This is mostly due to the lack of appropriate techniques that could nondestructively probe the silicone adhesive interface in situ.

We are using SFG to study the interfacial behavior of silicone adhesives at various polymer interfaces, focusing on the adhesion promoters. The SFG results can be well correlated to the adhesion strength measured using adhesion testing equipment, providing in-depth understanding on the interfacial structure-property relationships of different silicone materials.

In addition to SFG, molecular dynamics simulation was also used to study interfacial behavior of adhesion promoters in silicone adhesive formulation at buried interfaces.