Systematical Polymer Libraries

To understand the effect of molecular structure on the thermoresponsive OEGMA (co) polymers, polymer libraries were evaluated. By systematically varying the structure, for example, length or composition, of the copolymers followed by evaluation of the thermoresponsive properties, structure-property relationships are revealed. However, the preparation of such libraries of polymers can be very time consuming and is prone to human errors due to less-challenging repetition of similar experiments. Therefore, we have adapted the use of automated parallel synthesis robots for both the optimization of polymerization conditions as well as the preparation of polymer libraries (Hoogenboom et al, 2003 Meier et al, 2004). These synthesis robots will be discussed in this section as well as their use for the optimization of the RAFT polymerization process to demonstrate the added value of such equipment. 

At first, the RAFT polymerization with CBDB and AIBN was optimized in the automated parallel synthesis robot for the polymerization of MMA (Fijten et aL, 2004). The RAFT agent AIBN ratio was varied from I I to 1 0.05 for polymerizations in toluene at 70°C revealing uncontrolled polymerizations at a 1 1 ratio and very slow controlled polymerizations with a 

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In this chapter, we will focus on the use of CLP techniques for the synthesis of systematic copolymer libraries using high-throughput approaches. Prior to that, automated parallel optimization reactions that have been performed for different CLP techniques will be discussed. At the end of this chapter there will be a highlight on the latest synthetic approaches to synthesize well-defined polymer libraries. 

Before the preparation of systematical (co)polymer libraries to understand the effect of molecular structure on the thermoresponsive properties, the RAFT polymerization conditions were optimized using 2-cyano-2-butyl dithiobenzoate (CBDB) as RAFT agent and azobisi-sobutyronitrile (AIBN) as radical initiator. The RAFT polymerization mechanism and the structures of CBDB and AIBN are depicted in Figure 22.9. The control over the RAFT free-radical polymerization process strongly depends on the ratio of radical initiator to RAFT agent and temperature. Both these parameters control the number of radicals that are generated and, thus, influence the main propagation equilibrium, that is, the number of dormant and active chains in the system that controls the extent of termination reactions. 

Woodruff and co-workers introduced the expert system PAIRS [67], a program that is able to analyze IR spectra in the same manner as a spectroscopist would. Chalmers and co-workers [68] used an approach for automated interpretation of Fourier Transform Raman spectra of complex polymers. Andreev and Argirov developed the expert system EXPIRS [69] for the interpretation of IR spectra. EXPIRS provides a hierarchical organization of the characteristic groups that are recognized by peak detection in discrete ames. Penchev et al. [70] recently introduced a computer system that performs searches in spectral libraries and systematic analysis of mixture spectra. It is able to classify IR spectra with the aid of linear discriminant analysis, artificial neural networks, and the method of fe-nearest neighbors. 

The integrated DLS device provides an example of a measurement tool tailored to nano-scale structure determination in fluids, e.g., polymers induced to form specific assemblies in selective solvents. There is, however, a critical need to understand the behavior of polymers and other interfacial modifiers at the interface of immiscible fluids, such as surfactants in oil-water mixtures. Typical measurement methods used to determine the interfacial tension in such mixtures tend to be time-consuming and had been described as a major barrier to systematic surveys of variable space in libraries of interfacial modifiers. Critical information relating to the behavior of such mixtures, for example, in the effective removal of soil from clothing, would be available simply by measuring interfacial tension (ILT ) for immiscible solutions with different droplet sizes, a variable not accessible by drop-volume or pendant drop techniques [107]. 

Chitosan, the deacetylated form of chitin, is a plentiful and naturally occurring aminopolysaccharide obtained fl om shellfish and other marine species. Most of the research on applying this to fibers and films has been conducted in Japan and to a lesser extent Korea. Micromilled chitosan powder has been blended with rayon fibers, followed by subsequent lamination, to produce a variety of nonwoven fabrics known as Chitopoly. These modified materials were even effective against a methacillin-strain of S. aureus [37], Numerous other publications and patents describe incorporation of chitosan in various forms to produce antimicrobial fibers and polymers. One of the more recent examples is the binding of a quaternary ammonium derivative of chitosan to cotton fabric to produce an antibacterial finish [38]. The other area of current interest is the use of naturally occurring peptides as antimicrobial agents. The use of combinatorial libraries allows one to systematically examine ten to hundreds of millions of peptides for their antimicrobial activity. This was demonstrated with various strains... 

One of the major requirements related to combinatorial material research is, however, the preparation of thin films and dots from solution in a fast and reproducible manner. Furthermore, the parallel investigation of the physical properties of these films is required to develop a more detailed understanding and new structure-property relationships. Ink-jet printing can bridge the gap between polymer synthesis and solid-state or surface property evaluation, since the technique opens the way to the automatic preparation of libraries of polymers, polymer blends, and composites, with a systematic variation of parameters such as chemical composition or thickness." ... 

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