Soft Matter in Technology

Katharine Blodgett (Figure 9.1A), whose name is associated with Irvin Langmuir’s name for Langmuir–Blodgett (L–B) films, which are ordered molecular layers of amphiphilic molecules adsorbed on a solid surface (Section 6.2), had a peculiar life. Born in 1898 in New York state, she met Langmuir during a visit to the General Electric laboratories where her father worked. Then she went to Great Britain to do her PhD thesis with Ernest Rutherford (Nobel Prize in Chemistry in 1906). In 1926, she became the first woman to graduate with a doctorate in physics from Cambridge University. She then returned to the United States to work at General Electric as Langmuir’s assistant on organic monomolecular films (~3 nm) deposited on liquid. This work would allow Langmuir to be awarded the Nobel Prize in Chemistry in 1932. After forming calcium stearate films [(C₁₇H₃₅COO)₂Ca], Blodgett realized that, upon dipping a glass slide into the water and slowly removing it when the monomolecular film was formed on the water surface, the glass slide came out dry. This led Blodgett to propose that the hydrophilic heads (COO)₂ ^– Ca²⁺ attach to the glass by exposing the hydrophobic chain to air, which causes the water film to be withdrawn. From there, Langmuir and Blodgett were able to produce thicker films by successive soakings. Katharine Blodgett then understood the practical importance of these L–B layers in producing anti-reflective films on glass. General Electric patented the idea under the cryptic title “Film Structure and Method of Preparation” (U.S. patent 2,220,660 -16 March 1938), and Blodgett published in 1939 in Physical Review an article entitled “Using Interference to Turn Off the Reflection of Glass Light.” In particular, she showed an instrument with a glass dial illuminated by a stream of light, only half of which was treated with a L–B coating (Figure 9.1B). On the untreated part there is strong reflection and a dazzling effect which prevent the indications from being read, and this is not the case for the part treated with anti-reflection coating. Figure 9.1 (A) Photograph showing Katharine Blodgett at work in front of a Langmuir trough. (B) Photograph taken from Katharine Blodgett’s article showing the anti-reflective effect. (C) Working principle of anti-reflective treatments. https://s3-euw1-ap-pe-df-pch-content-public-u.s3.eu-west-1.amazonaws.com/9780429154355/75121c3f-9fce-4f28-b106-96ade177249e/content/fig9_1_PB.tif" xmlns:xlink="https://www.w3.org/1999/xlink"/> https://s3-euw1-ap-pe-df-pch-content-public-u.s3.eu-west-1.amazonaws.com/9780429154355/75121c3f-9fce-4f28-b106-96ade177249e/content/fig9_1_OC.tif" xmlns:xlink="https://www.w3.org/1999/xlink"/>