2-cinnamoylethyl Methacrylate Research Articles

Chain Exchange Kinetics of Polystyrene-block-poly(2-cinnamoylethyl methacrylate) Micelles in THF/Cyclopentane Mixtures

Two to three pyrene groups were attached to the PCEMA block of polystyrene-block-poly(2-cinnamoylethyl methacrylate) (PS-b-PCEMA) to yield PS-b-PCEMA−Py. Both PS-b-PCEMA and PS-b-PCEMA−Py formed micelles with PCEMA cores and PS shells in THF/cyclopentane (CP) mixtures with sufficiently high CP contents. Mixing such micelles led to chain exchange between different micelles, which increased the pyrene monomer fluorescence intensity at the cost of excimer emission. The data of pyrene monomer fluorescence intensity increase with time and were fitted to a two-exponential-term function. The average lifetime obtained was used to characterize the micelle chain exchange rate. Investigated were the effect of varying solvent composition, temperature, micelle concentration, and the length of both the PS and PCEMA blocks on the chain exchange rate.

Multiple morphologies of polyisoprene- block-poly(2-cinnamoylethyl methacrylate) and polystyrene- block-poly (2-cinnamoylethyl methacrylate) micelles in organic solvents

Polyisoprene- block-poly(2-cinnamoylethyl methacrylate) (PI- b-PCEMA) and polystyrene- block-poly(2-cinnamoylethyl methacrylate) (PS- b-PCEMA) formed micelles in solvents, such as cylcopentane (CP), which were selectively poor for PCEMA. Decreasing the length of the soluble blocks relative to that of PCEMA, the shape of the micelles changed from spheres, to cylinders, and to vesicles for both families of diblock copolymers. When a binary solvent mixture was used, the same micellar morphological transitions could be induced for the same diblock by increasing the content of the block selective solvent in the mixture. For PI- b-PCEMA, this meant an increase in the content of hexanes (HX) in THF/HX where HX was good only for PI. Similar trend was observed for PS- b-PCEMA in THF/CP. This represented the first observation of multiple morphologies of diblock copolymer micelles formed in organic solvents.

Cross-Linked Nanospheres of Poly(2-cinnamoylethyl methacrylate) with Immediately Attached Surface Functional Groups

A polyisoprene-block-poly(2-cinnamoyethyl methacrylate) (PI-b-PCEMA) sample with a narrow molar mass distribution was prepared and characterized. The sample formed spherical micelles in hexanes/THF with 20% of THF by volume. After photo-cross-linking of the PCEMA core took place, the PI corona block was cleft by ozone and (CH3)3P treatment to produce PCEMA nanospheres with surface carbonyl groups or PCEMA−CO nanospheres. These spheres were stable without any added surfactant in a good solvent for PCEMA. Reaction of the carbonyl groups with cyclopentadiene catalyzed by pyrrolidine yielded fulvene-covered nanospheres, PCEMA−FV nanospheres, which possessed better solubility in organic solvents than the PCEMA−CO spheres. This work represents the first attempt at the preparation of cross-linked nanospheres with immediately attached surface functional groups from block copolymers. When appropriately functionalized, these nanospheres should be useful as solid lubricant or support for catalysts.

Star and Cylindrical Micelles of Polystyrene-block-poly(2-cinnamoylethyl methacrylate) in Cyclopentane

Polystyrene-block-poly(2-cinnamoylethyl methacrylate) (PS-b-PCEMA) samples with n/m larger than 9.0, where n and m stand for the numbers of styrene and of CEMA units in a chain, formed essentially star micelles and those with n/m between 7 and 8.2 formed mixtures of star and long cylindrical micelles in cyclopentane with PCEMA as the core and PS as the shell. UV cross-linking of the PCEMA cores of these micelles at 50 °C yielded star polymers and nanofibers. This probably represents the first preparation of cross-linked block copolymer cylindrical micelles or nanofibers in the solution phase. While we have previously prepared star polymers using this approach, this study shows the robustness of this method in producing star polymers with as many as 4.5 × 102 arms and a molar mass of 9.9 × 107 g/mol. Detailed study showed that UV cross-linking only locked in the structure of the micelles and did not change their aggregation numbers. This allowed us to determine the molar masses of the cross-linked micelles...

Formation and Properties of Polystyrene-block-poly(2-cinnamoylethyl methacrylate) Brushes Studied by Surface-Enhanced Raman Scattering and Transmission Electron Microscopy

The aliphatic double bond of poly(2-cinnamoylethyl methacrylate) (PCEMA) displayed a characteristic surface-enhanced Raman scattering (SERS) peak at 1640 cm-1. Polystyrene (PS), together with the phenyl rings of PCEMA, contributed to the peak at 1005 cm-1. We determined the intensity ratio of these two peaks, i.e. I1640/I1005, for PS-b-PCEMA films deposited, from THF/cyclopentane (CP) mixtures, on silver and silicate-covered silver (or silica) surfaces. In THF/CP with CP volume fractions, fCP, between 0.60 and 0.90, the I1640/I1005 values were large. Since only these species which are in the immediate neighborhood of a roughened metal substrate, e.g. within ∼100 Å, yield SERS responses, these data suggest that PS-b-PCEMA were adsorbed by silica and silver in the brush conformation, with PCEMA as the anchoring layer and PS as the buoy layer, in THF/CP with fCP between 0.60 and 0.90. At low fCP's, PS-b-PCEMA samples did not adsorb on silica but did on silver. SERS results suggest that the adsorption on silver might be via either styrene or CEMA as the anchoring group. At high fCP's, PS-b-PCEMA micelles adsorbed. Brush formation at intermediate fCP and micelle adsorption at high fCP were directly confirmed by transmission electron microscopy for one of our PS-b-PCEMA samples. SERS results also suggest one of the possible mechanisms for PS-b-PCEMA adsorption was via the anchoring of micelles first. The micelles subsequently disintegrated on an adsorbate if fCP was not too high and the rate for micelle dissociation was sufficiently fast.

Water-Soluble Nanospheres of Poly(2-cinnamoylethyl methacrylate)-block-poly(acrylic acid)

Poly(2-cinnamoylethyl methacrylate)-block-poly(acrylic acid) (PCEMA-b-PAA), with PCEMA photo-cross-linkable and PAA water soluble, were synthesized and characterized. The polymer formed spherical micelles in DMF/water with PCEMA as the core and PAA as the corona. The photo-cross-linking of the micelles yielded water-soluble nanospheres. The nanospheres were characterized by transmission electron microscopy (TEM) and light scattering. Dynamic light-scattering studies revealed that the nanospheres could readily take up organics in water. Coagulation of the nanospheres could be induced by the addition of divalent cations. These properties may allow the use of the nanospheres as the traps for organics in contaminated waters.

Adsorption of Polystyrene-block-poly(2-cinnamoylethyl methacrylate) by Silica from Block-Selective Solvent Mixtures

Polystyrene-block-poly(2-cinnamoylethyl methacrylate) (PS-b-PCEMA) of different block lengths have been synthesized. These polymers were adsorbed via the anchoring of the insoluble PCEMA block on silica, in the brush conformation, from cyclohexane/THF or cyclopentane/THF mixtures when cyclohexane or cyclopentane contents were high. The adsorbed amount could be increased or decreased by increasing or decreasing the cyclohexane or cyclopentane content. In a given solvent mixture, number surface coverages ρ∞ increased as n/m decreased, where n and m are the numbers of repeat units for the PS and PCEMA blocks, respectively. The trend that ρ∞ increased with decreasing n/m is contradictory to previous experimental observations but can be well explained by the scaling relation derived by Marques et al. for block copolymer adsorption from a micellar solution in the buoy-dominated regime.

Star Polymers and Nanospheres from Cross-Linkable Diblock Copolymers

Polystyrene-block-poly(2-cinnamoylethyl methacrylate) (PS-b-PCEMA) formed micelles in THF/cyclohexane or chloroform/cyclohexane mixtures with the PCEMA block as the core. Depending on the relative length of the PS and PCEMA block, star and crewcut micelles were prepared. Upon UV irradiation, the PCEMA block selectively cross-linked to form star polymers and nanospheres from the corresponding star and crewcut micelles. The cross-linked micelles were characterized by solution and solid-state NMR, FTIR, GPC, TEM, and dynamic and static light scattering.

Polystyrene-block-poly(2-cinnamoylethyl methacrylate) Adsorption in the van der Waals−Buoy Regime

Polystyrene-block-poly(2-cinnamoylethyl methacrylate) (PS-b-PCEMA) polymers of different asymmetric ratios, β, and numbers, m, of CEMA units were synthesized and characterized. In cyclopentane/THF mixtures, the polymers were adsorbed by silica mainly via the PCEMA block in the brush conformation. For samples with β values greater than 4, their surface adsorption data could be well explained by the theory of Marques et al. for diblock adsorption from micelle solutions in the van der Waals−buoy regime. This represents the first experimental confirmation of such a scaling relation. On silver surfaces, the PCEMA block was the main adsorbing species for samples with small β and large m, and both the PS and PCEMA blocks adsorbed for samples with large β and small m values. As polymer brushes are not formed from certain polymers, the data of polymer adsorption by silver did not follow the scaling relation of Marques et al.