Functionalization Gradient copolymers

The limit of detection for this instrument is about 10 pg/ ml for polystyrene in 2-butanone,163 which is close to two orders of magnitude higher than that of the deflection-type DRI. Moreover, the response of the ELSD is linear over only two decades in concentration.163 The ELSD is a useful backup detector when the DRI or UV detectors are not appropriate, e.g., when the UV absorbance or RI change is a function of copolymer composition as well as concentration or in gradient elution systems where changes in solvent composition cause drift in baselines of the UV and DRI detectors. Compounds about as volatile as the solvent are poorly detected by ELSD. 

Figure 14. The phase diagram of the gradient copolymer melt with the distribution functions g(x) = l — tanh(ciit(x —fo)) shown in the insert of this figure for ci = 3,/o = 0.5 (solid line), and/o — 0.3 (dashed line), x gives the position of ith monomer from the end of the chain in the units of the linear chain length. % is the Flory-Huggins interaction parameter, N is a polymerization index, and/ is the composition (/ = J0 g(x) dx). The Euler characteristic of the isotropic phase (I) is zero, and that of the hexagonal phase (H) is zero. For the bcc phase (B), XEuier = 4 per unit cell for the double gyroid phase (G), XEuier = -16 per unit cell and for the lamellar phases (LAM), XEuier = 0.

A number of different types of copolymers are possible with ATRP—statistical (random), gradient, block, and graft copolymers [Matyjaszewski, 2001]. Other polymer architectures are also possible—hyperbranched, star, and brush polymers, and functionalized polymers. Statistical and gradient copolymers are discussed in Chap. 6. Functionalized polymers are discussed in Sec. 3-16b. 

Polymers prepared via CRP show promise for applications like photoresists [112], liquid-crystalline displays [147-149, 154], and photo catalysts [151]. Incorporating blocks prepared using CRP techniques into copolymers with conductive or luminescent blocks [240,241,243,251] may impart better processability and make them useful for a broader range of applications. Block or gradient copolymers with highly controlled compositions may also be industrially useful as blend compatibilizers or as surfactants [194],perhaps improving upon already existing materials. Well-defined or functional compatibilizers and stabilizers could potentially result in lower production costs if less material is needed to impart the desired properties. 

By living cationic polymerization, our group has investigated the synthesis of polymers of various shapes including gradient copolymers,PVA graft copolymers,and end-functional polymers for the modification of liposomes to provide controlled release of drugs. 

Figure 21 (a) Solubility overview for the PNonOx-sfaf-PPhOx gradient copolymers in ethanol-water mixtures (5 mg mP ). (b) Cloud point (UCST) as function of monomer composition and solvent mixture determined at 5.0 mg ml Reprinted from Hoogenboom, R. Lambermont-Thijs, H. M. L. Jochems, M. J. H. C. etal. Soft Matter2009,5,3590-3592. Reproduced by permission of the Royal Society of Chemistry. 

Due to the high level of end-group functionality and the lifetime of the polymer chains, NMP is an attractive methodology for synthesizing not only homopolymers but also block copolymers and well-defined gradient copolymers. 

Seymour and coworkers (27,28,29,30) actually used these composition gradients to prepare block copolymers by swelling particles containing occluded (i.e., living) macroradicals with a second monomer. Such block copolymers were prepared from occluded vinylacetate, methyl methacrylate, and acrylonitrile macroradicals, and the yield of block copolymers was studied as a function of the solubility and rate of diffusion of the swelling monomer in the particles. 

Fig. 5.25 Temperature gradient, conductive heat flux, convective heat flux, and heat flux by chemical reaction as a function of distance from the burning surface at 3 MPa (initial temperatures 243 K and 343 K) for BAMO/ THF = 60 40 copolymer.

Fig. 16 Representative data from the surface wrinkling metrology, demonstrating the unprecedented range of moduli and the precision that the methodology unlocks a modulus of a thickness gradient library of PS (reproduced with permission from [72]) b modulus as a function of composition for P(S-I-S) triblock copolymer blends c modulus as a function of thickness for ultrathin PS films (reproduced with permission from [74]). The lines are meant to guide the eye and the error bars represent one standard deviation of the data, which is taken as the experimental uncertainty of the measurement...

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