The mean-square radius of gyration 〈S 2 〉 was determined from small-angle X-ray and light scattering measurements for 20 samples of atactic oligo-and poly(R-methylstyrene)s (a-PRMS), each with the fraction of racemic diads fr ) 0.72, in the range of weight-average molecular weight from 6.48 × 10 2 (pentamer) to 3.22 × 10 6 in cyclohexane at 30.5°C (Θ). The ratio 〈S 2 〉/xw as a function of the weightaverage degree of polymerization xw first increases steeply for xw j 20, then passes through a flat hump at xw = 40, and finally approaches its asymptotic value for xw J 1 ×10 3 . On the basis of the helical wormlike (HW) chain model the HW model parameters are λ -1 κ0 ) 3.0, λ -1 τ0 ) 0.9, λ -1 ) 46.8 Å, and ML ) 39.8 Å -1 , where κ0 and τ0 are the differential-geometrical curvature and tortion, respectively, of the characteristic helix of the HW chain taken at the minimum zero of its elastic energy, λ -1 is the stiffness parameter, and ML is the shift factor defined as the molecular weight per unit contour length of the chain. The local chain conformations of a-PRMS are discussed in detail on the basis of the above values of the model parameters and compared with those of atactic polystyrene (fr ) 0.59), atactic poly(methyl methacrylate) (a-PMMA) (fr ) 0.79), and isotactic PMMA (fr = 0.01) previously studied. It is then concluded that the a-PRMS chain tends to retain large and clearly distinguishable helical portions in dilute solution like the a-PMMA chain, as was expected from their chemical structures, although the helical nature of the former is somewhat weaker. To illustrate the situation, pictures are given of representative instantaneous contours of HW Monte Carlo chains for the above four polymers.

The cloud point was determined for aqueous solutions of four kinds of poly(N-isopropylacrylamide) samples synthesized by radical polymerization in methanol, tert-butanol, benzene, and 1,4-dioxane by the use of azobis(isobutyronitrile) as an initiator, in the range of the weight fraction of the sample from 0.5 to 10%. It has then been found that the cloud points so determined for the samples synthesized in benzene and 1,4-dioxane are definitely lower than those for the samples synthesized in methanol and tert-butanol, although all the samples have almost the same stereochemical composition and the same end group. The observed deviation may be regarded as arising from the difference in the primary structure between the samples.

The intrinsic viscosity [η] was determined for 23 samples of atactic oligo-and poly(Rmethylstyrene)s (a-PRMS), each with the fraction of racemic diads fr ) 0.72, in the range of weightaverage molecular weight Mw from 4.12 × 10 2 to 5.46 × 10 6 in three good solvents, toluene, 4-tert-butyltoluene, and n-butyl chloride, at 25.0 °C. The translational diffusion coefficient D was also determined from dynamic light-scattering measurements for 17 a-PRMS samples in the range of Mw from 1.04 × 10 3 to 3.22 × 10 6 under the same solvent conditions. It was found that the values of [η] in toluene and n-butyl chloride are appreciably smaller than the previous ones of [η]Θ in cyclohexane at 30.5 °C (Θ) in the oligomer region in which the intramolecular excluded-volume effect may be ignored, while those of [η] in 4-tert-butyltoluene are only slightly larger than the latter there because of the dependence on solvent of the hydrodynamic chain (bead) diameter. The disagreement in toluene and n-butyl chloride may be regarded as arising from the so-called specific interaction between polymer and solvent molecules, and therefore the viscosity-radius expansion factor R η in these solvents was calculated after removing its contribution. On the other hand, the values of the hydrodynamic radius RH defined from D in the three good solvents were found to agree well with the previous ones of RH,Θ in cyclohexane at Θ in the oligomer region, and therefore the hydrodynamic-radius expansion factor RH could be calculated straightforwardly. It was then found that both plots of Rη and RH against the scaled excluded-volume parameter z ˜for a-PRMS in the three good solvents along with those for atactic polystyrene and atactic and isotactic poly(methyl methacrylate)s previously studied form their respective single-composite curves, confirming the validity of the quasi-two-parameter scheme that all expansion factors are functions only of z ˜irrespective of the differences in polymer species (chain stiffness and local chain conformation) and solvent condition.

We report the controlled radical polymerization of 2-vinyl-4,4-dimethyl azlactone (VDMA), a 2-alkenyl-2-oxazolin-5-one monomer that contains a polymerizable vinyl moiety and a highly reactive, pendant azlactone, as well as dilute solution properties and surface attachment and functionalization. Reversible addition−fragmentation chain transfer (RAFT) was used to polymerize VDMA in benzene at 65 °C using either 2-(2-cyanopropyl) dithiobenzoate (CPDB) or 2-dodecylsulfanylthiocarbonylsulfanyl-2-methylpropionic acid (DMP) as RAFT chain transfer agents (CTAs). The pseudo-first-order kinetics and resultant well-defined polymers of low polydispersity indicate that both CTAs afford control over the RAFT polymerization of VDMA. Dynamic and static light scattering and small-angle neutron scattering (SANS) were performed to determine the weight-average molecular weight, radius of gyration, and second virial coefficient of VDMA homopolymers in THF. Additionally, well-defined polymers of VDMA containing carboxyl end groups were covalently attached to epoxy-modified silicon wafers via esterification to produce polymeric scaffolds that can be subsequently functionalized for various bio-inspired applications.