Microfluidic methodologies are becoming increasingly important for rapid formulation and screening of materials, and development of analytical tools for multiple sample screening is a critical step in achieving a combinatorial 'lab on a chip' approach. This work demonstrates the application of Raman spectroscopy for analysis of monomer composition and degree of conversion of methacrylate-based droplets in a microfluidic device. Droplet formation was conducted by flow focusing on the devices, and a gradient of component composition was created by varying the flow rates of the droplet-phase fluids into the microchannels. Raman data were collected using a fiber optic probe from a stationary array of the droplets/particles on the device, followed by partial least squares (PLS) calibration of the first derivative (1600 cm 21 to 1550 cm 21 ) allowing successful measurement of monomer composition with a standard error of calibration (SEC) of ¡1.95% by volume. Following photopolymerization, the percentage of double bond conversion of the individual particles was calculated from the depletion of the normalized intensity of the CLC stretching vibration at 1605 cm 21 . Raman data allowed accurate measurement of the decrease in double bond conversion as a function of increasing crosslinker concentration. The results from the research demonstrate that Raman spectroscopy is an effective, on-chip analytical tool for screening polymeric materials on the micrometre scale.

No abstract

A stable solution composition gradient is generated inside a microchannel by varying the relative flow rates of two solutions that differ in composition. This solution gradient is used to synthesize a surface‐grafted statistical‐copolymer‐brush composition gradient via surface‐initiated atom transfer radical polymerization (ATRP; see schematic). Near‐edge absorption fine structure spectroscopy confirms the continuous transition of surface composition from one end of the substrate to the other.

Over the last decade, there has been an increased drive in the polymer industry toward the development of in-line monitoring techniques for analysis of melt processing. Manufacture of high material volumes combined with stringent quality-control restrictions and the requirement for tailored end-user products, have made the implementation of analytical methods essential for measurement of material characteristics. This paper presents the application of a range of spectroscopic techniques for in-line analysis of polymer extrusion processes. Fourier transform near-infrared (FT-NIR), Raman and fluorescence spectroscopy have been successfully implemented as tools to monitor a range of processing characteristics including copolymer melt and additive composition, material residence time distribution and degree of polymerization. In combination with partial least squares (PLS) chemometric analysis, these spectroscopic techniques are demonstrated to be sensitive and robust tools for monitoring a wide range of chemical and physical parameters at high-temperature and pressure in a polymerprocessing environment.

No abstract