The reduced chain entanglement of brush polymers over their linear analogs drastically lowers the energetic barriers to reorganization. In this report, we demonstrate the rapid self-assembly of brush block copolymers to nanostructures with photonic bandgaps spanning the entire visible spectrum, from ultraviolet (UV) to near infrared (NIR). Linear relationships were observed between the peak wavelengths of reflection and polymer molecular weights. This work enables "bottom-up" fabrication of photonic crystals with application-tailored bandgaps, through synthetic control of the polymer molecular weight and the method of self-assembly. These polymers could be developed into NIR-reflective paints, to combat the "urban heat island effect" due to NIR photon thermalization.

Self-assembled structures of brush block copolymers (BrBCPs) with polylactide (PLA) and polystyrene (PS) side chains were studied. The polynorbornene-backbone-based BrBCPs containing approximately equal volume fractions of each block self-assembled into highly ordered lamellae with domain spacing ranging from 20 to 240 nm by varying molecular weight of the backbone in the bulk state, as revealed by small-angle X-ray scattering (SAXS). The domain size increased approximately linearly with backbone length, which indicated an extended conformation of the backbone in the ordered state. In situ SAXS measurements suggested that the BrBCPs self-assemble with an extremely fast manner which could be attributed to a reduced number of entanglements between chains. The strong segregation theory and Monte Carlo simulation also confirmed this near-linear dependence of the domain spacing on backbone length, rationalizing experimental results.

We describe a simple route to fabricate two dimensionally well-ordered, periodic nanopatterns using the self-assembly of brush block copolymers (brush BCPs). Well-developed lamellar microdomains oriented perpendicular to the substrate are achieved, without modification of the underlying substrates, and structures with feature sizes greater than 200 nm are generated due to the reduced degree of chain entanglements of brush BCPs. A near-perfect linear scaling law was found for the period, L, as a function of backbone degree of polymerization (DP) for two series of brush BCPs. The exponent increases slightly from 0.99 to 1.03 as the side chain molecular weight increases from ∼2.4 to ∼4.5 kg/mol–1 and saturated with further increase in the side chain molecular weight due to the entropic penalty associated with the packing of the side chains. Porous templates and scaffolds from brush BCP thin films are also obtained by selective etching of one component.

In this report, we explore the capability of macromolecules to interdigitate into densely grafted molecular brush copolymers. We demonstrate that by using the tendency for stereocomplexation between poly(l-lactide) and poly(d-lactide) as a driving force complementary linear polymers and brush copolymers can form a stereocomplex. However, stereocomplex formation between complementary brush copolymers is restricted and only partially observed when the side chains are of a critical molecular weight.

Conductive fullerene (C 60 ) units were designed to be arranged in one dimensional close contact by locally organizing them with covalent bonds in a spatially constrained manner. Combined molecular dynamics and quantum chemical calculations predicted that the intramolecular electronic interactions (i.e. charge transport) between the pendant C 60 units could be controlled by the length of the spacers linking the C 60 units and the polymer main chain. In this context, C 60 side-chain polymers with high relative degrees of polymerization up to 1220 and fullerene compositions up to 53% were synthesized by ruthenium catalyzed ring-opening metathesis polymerization of the corresponding norbornene-functionalized monomers. UV/vis absorption and photothermal deflection spectra corroborated the enhanced interfullerene interactions along the polymer chains. The electron mobility measured for the thin film fieldeffect transistor devices from the polymers was more than an order of magnitude higher than that from the monomers, as a result of the stronger electronic coupling between the adjacent fullerene units within the long polymer chains. This molecular design strategy represents a general approach to the enhancement of charge transport properties of organic materials via covalent bond-based organization.

In Figure 4A,B, the power law exponent for Case I (lower molecular weight brushes, 2.4K) was reported to be 0.84 when, in fact, the exponent should have been 0.93, and for Case II (higher molecular brushes, 4.5K), the exponent was reported to be 0.91, when the exponent should have been 0.82. The corrected Figure 4A,B is given below.Based on the incorrectly calculated slopes, we made the statement, "Since group II BrBCPs have longer side chains compared with group I, steric hindrance may make the backbone more rigid and, thus, cause the value to be even larger", which is also not correct. Rather, in theory, the reason that the exponent is larger for smaller side chain relates to the dominance of side chain elasticity over interfacial energy contribution. The backbone will stretch to minimize the interfacial area (per unit volume), which decreases the cross-sectional area of the brush at the interface. The stretching is energetically more costly for the higher molecular weight brushes, which leads to

This study explores the importance of general chemistry as a prerequisite for organic chemistry lecture courses. The students taking organic chemistry were categorized into three groups: (1) those who had finished the prerequisite before starting organic chemistry, (2) those who had not finished the prerequisite before starting organic chemistry, and (3) those who were repeating the course. Most students in group 2, however, took general chemistry during the same semester. The general chemistry prerequisite was found to have a positive but minimal impact on student performance, yielding a slightly improved average and pass rate. However, the difference between groups 1 and 2 was not statistically significant. These results raise the question of whether or not general chemistry should be viewed as a required prerequisite. A few more responses to the implications of these results are offered including using placement exams and AP/IB scores to evaluate whether students require the prerequisite and using intended learning outcomes strategically when designing curricula. Lastly, these results can remind us, as instructors, of being aware of the assumptions we make about our students' knowledge and academic preparedness.

In this study, the effect of 18-crown-6 on the stability of oxytocin in aqueous solution was explored. The study found that while 12-crown-4 and 15crown-5 do not stabilize oxytocin, 18-crown-6 does have a stabilizing effect in citrate/phosphate buffer at pH 4.5. However, in acetate buffer at the same pH, the presence of 18-crown-6 had a destabilizing effect, possibly leading to a different degradation pathway. Both the stabilizing and destabilizing effects, depending on the buffer used, are concentration dependent where a higher concentration of 18crown-6 is linked to a stronger effect. It is hypothesized that this effect may be linked to 18-crown-6 binding to the protonated ammonium group of oxytocin. Upon changing the mobile phase used in highperformance liquid chromatography experiments, we observed evidence supporting this binding hypothesis. When an acidic mobile phase was used (0.01% trifluoroacetic acid (TFA)), a partial shift in oxytocin retention time was observed for samples in acetate buffers in the presence of 18-crown-6 when using a 150 mm column (C18). The amount of the peak that shifted depended on the 18-crown-6 concentration used. A similar shift in oxytocin peak retention time was observed for samples in both acetate and citrate/ phosphate buffers when using a 250 mm column (C18), but the peak completely shifted in those samples. When using an even more acidic mobile phase (0.1% TFA), the oxytocin peaks all had the same retention time again. Ultraviolet and nuclear magnetic resonance spectroscopy experiments also showed that the presence of 18-crown-6 has an observable effect on the resulting oxytocin spectra.