Phase behavior of solvent vapor annealed thin films of PS-b-P4VP(PDP) supramolecules van Zoelen, Wendy; Asumaa, Terhi; Ruokolainen, Janne; Ikkala, OlliI; ten Brinke, Gerrit Take-down policy If you believe that this document breaches copyright please contact us providing details, and we will remove access to the work immediately and investigate your claim.Downloaded from the University of Groningen/UMCG research database (Pure): http://www.rug.nl/research/portal. For technical reasons the number of authors shown on this cover page is limited to 10 maximum. FIN-02015 HUT Espoo, Finland ReceiVed December 13, 2007; ReVised Manuscript ReceiVed February 12, 2008 ABSTRACT: The phase behavior and terrace formation of solvent (chloroform) vapor annealed thin films of asymmetric comb-shaped supramolecules consisting of a polystyrene (PS) block and a supramolecular block of poly(4-vinylpyridine) (P4VP) hydrogen bonded with pentadecylphenol (PDP) on silicon oxide (SiO 2 ) were examined. P4VP(PDP) was found to be present at the SiO 2 interface as well as the air interface, implying symmetric boundary conditions. Because of the inherent change in composition by swelling in a selective solvent, the morphology of a lamellar film could be changed to cylindrical by swelling at different vapor pressures of chloroform vapor. Swelling at a specific vapor pressure at the phase boundary between lamellar and cylindrical resulted in noncommon terrace formation behavior. The lowest terrace consisted of two wetting layers forming one lamella, the second terrace contained perpendicular lamellae, and the highest terrace consisted of parallel P4VP(PDP) cylinders. The results are presented in a morphology diagram as a function of film thickness and composition.

Amphiphilic polymers, specifically combinations of hydrophilic and hydrophobic residues, have been shown to be effective as antifouling materials against the algae Ulva linza and Navicula diatoms. Here we use the inherent sequence specificity of polypeptoids made by solid-phase synthesis to show that the sequence of hydrophilic (methoxy) and hydrophobic (fluorinated) moieties affects both antifouling and fouling release of U. linza. The platform used to test these sequences was a polystyrene-bpoly(ethylene oxide-co-allyl glycidyl ether) (PS-b-P(EO-co-AGE)) scaffold, where the polypeptoids are attached to the scaffold using thiol−ene click chemistry. The fluorinated moiety is very surface active and directs the surface composition of the polymer thin film. The position and number of fluorinated groups in the polypeptoid are shown to affect both the surface composition and antifouling properties of the film. Specifically, the position of the fluorinated units in the peptoid chain changes the surface chemistry and the antifouling behavior, while the number of fluorinated residues affects the fouling-release properties.

The monomer conversion dependence of the formation of the various types of defect structures in radical suspension polymerization of vinyl chloride was examined via both 1H and 13C NMR spectrometry. The rate coefficients for model propagation and intra- and intermolecular hydrogen abstraction reactions were obtained via high-level ab initio molecular orbital calculations. An enormous increase in the formation of both branched and internal unsaturated structures was observed at conversions above 85%, and this is mirrored by a sudden decrease in stability of the resulting PVC polymer. Above this threshold-conversion, the monomer is depleted from the polymer-rich phase, and the propagation rate is thus substantially reduced, thereby allowing the chain-transfer processes to compete more effectively. In contrast to the other defects, the chloroallylic end groups were found to decrease at high conversions. On the basis of the theoretical and experimental data obtained in this study, this decrease was attributed to copolymerization and abstraction reactions that are expected to be favored at high monomer conversions. Finally, a surprising increase in the concentration of the methyl branches was reported. Although a definitive explanation for this behavior is yet to be obtained, the involvement of transfer reactions of an intra- or intermolecular nature seems likely, and (in the latter case) these could lead to the presence of tertiary chlorine in these defects.

Due to their ability to microphase separate into well ordered structures with periodicities on the nanometre scale, block copolymers have received widespread attention as building blocks for the fabrication of nanomaterials. In particular, thin films of block copolymers promise new technological breakthroughs in e.g. computer memory applications. This Review gives a short overview of progress that has been made in preparing suitable thin films of conventional coil-coil diblock copolymer systems, while the advantages as well as the complexities of using more unconventional systems such as triblock copolymers and supramolecular systems are emphasized. Gerrit tenBrinke obtained his PhD in Statistical Physics from the University of Groningen, The Netherlands. He spent two years as a postdoctoral fellow at the University of Massachusetts at Amherst. In 1985 he became Associate Professor in the Polymer Department of the University of Groningen and in 1996 Professor. During 1994-1999 he was also part time Professor at the Helsinki University of Technology working closely together with Olli Ikkala. His research interests are self-assembly in complex polymer systems.

The terrace formation behavior of chloroform vapor annealed thin films of asymmetric, low molecular weight comb-shaped supramolecules consisting of a short polystyrene (PS) block and a long supramolecular block of poly(4-vinylpyridine) (P4VP) hydrogen bonded with pentadecylphenol (PDP) on silicon oxide (SiO 2) was examined with atomic force microscopy. During annealing, PS microphase separated from the disordered P4VP(PDP) comb, resulting in the formation of terraces of parallelly oriented microdomains of PS in a matrix of P4VP. Upon evaporation of the solvent, the P4VP(PDP) combs dropped below their order-disorder transition, and formed alternating layers of P4VP and PDP, which for high P4VP(PDP) fractions were also oriented parallel to the substrate. This resulted in terraces of the short P4VP(PDP) length scale within terraces of the PS-P4VP long length scale. Washing away PDP from the thin films with ethanol provided an effective means of studying the morphology of the lowest terrace of the thin films and, for a particular system, also resulted in a uniform monolayer of cylinders with a PS core and a P4VP corona.

Tunability of polymer surface properties depends crucially on both the chemical composition of the polymer and the physics of the chains (e.g., surface segregation, chain shape, etc.). Polypeptoids, which are non-natural biomimetic polymers based on an N-substituted glycine backbone, provide a flexible model system in which monomer sequence, chain shape, and self-assembled structure can easily be controlled to understand their influence on surface properties. We demonstrate the influence of the amount and sequence of hydrophobic monomers in a predominantly hydrophilic peptoid chain on the surface properties of a hybrid block copolymer, poly(peptoid-b-styrene). Just three fluorinated groups in peptoid sequences consisting of up to 45 hydrophilic monomers in length were needed to lower the surface energy of the peptoid and allow for its maximal surface segregation. Positioning these fluorinated groups in the middle of a chain as opposed to the chain ends resulted in a change in chain conformation at the surface as evidenced by near-edge X-ray absorption fine structure spectroscopy (NEXAFS). Surface reconstruction of polymers containing only three fluorinated monomers occurred within seconds but could be slowed by an order of magnitude when five fluorinated monomers were incorporated.

Self-assembled blends of PS-b-P4VP(PDP) supramolecules, obtained by hydrogen bonding of pentadecylphenol (PDP) side chains to poly(4-vinylpyridine), and poly(2,6-dimethyl-1,4-diphenyl oxide) (PPE) were investigated by thermal analysis and small-angle X-ray scattering (SAXS) and compared with blends of PS-b-P4VP and PPE. Differential scanning calorimetry (DSC) measurements showed a single composition dependent T g of the PPE/PS layers for both systems, demonstrating that PPE is distributed throughout the PS layers. Furthermore, DSC showed that for the PPE/PS-b-P4VP(PDP) blends the presence of PDP is not restricted to the P4VP layers. Its partial presence in the PS-containing domains was confirmed by nuclear magnetic resonance (NMR) spectroscopy on PS-P4VP core-corona nanorods prepared from hexagonally self-assembled PS-b-P4VP-(PDP) supramolecules. The results of the SAXS study on the dependence of the lamellar period of PPE/PS-b-P4VP blends on the amount of PPE were in excellent agreement with a theoretical model based on the Alexander-De Gennes approximation assuming a uniform distribution of PPE throughout the PS layers. For PPE/PS-b-P4VP(PDP) blends the dependence of the long period on the amount of PPE turned out to be somewhat stronger, which may be related to the supramolecular comb-shaped nature of the P4VP(PDP) blocks.

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