A new type of macromolecular architecture, denoted as dendrimer-like star block copolymers, is reported. These block copolymers are described by a radial geometry where the different generations or layers are comprised of high molecular weight polymer emanating from a central core. A hexahydroxyl functional core was used as an initiator for the “living” ring opening polymerization (ROP) of ε-caprolactone producing a hydroxyl terminated six arm star polymer with controlled molecular weight and narrow polydispersities (PD < 1.1). Capping these chain ends with dendrons containing activated bromide moieties produced “macro-initiators” for atom transfer radical polymerization (ATRP). Methyl methacrylate was polymerized from these “macro-initiators” in the presence of an organometallic promoter to produce the requisite dendrimer-like star polymers. High molecular weight was obtained with low polydispersities (<1.2). Alternatively, amphiphilic character could be introduced by designing the different layers or generations to be either hydrophobic or hydrophilic. For example, methyl methacrylate (MMA) with either hydroxyethyl methacrylate (HEMA) or methacrylate functional ethylene oxide macromonomers (EO) were polymerized from these “macro-initiators” to provide a hydrophilic outer layer. The use of macromolecular building blocks allows rapid attainment of high polymer in a limited number of steps with purification between transformation requiring only polymer precipitation.

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The synthesis of novel poly(methyl methacrylate)s with starlike architectures by controlled radical polymerization starting from dendritic 2-, 4-, 6-, and 12-arm multifunctional initiators is described. The more highly functionalized initiators were obtained by coupling a bromo-functionalized bis-(hydroxymethyl)propionic acid (bis-MPA) first generation dendron to hydroxyl-functionalized precursors. The controlled free radical character of the atom transfer radical polymerization is supported by the remarkably low polydispersities of the polymers and the close correspondence between the calculated and measured molecular weights. NMR studies on the polymers were consistent with initiation occurring from all initiator arms for the 2-, 4-, and 6-arm derivatives. Initial studies on deuterated polymers derived from 12-arm initiator suggest that in some cases initiation was not quantitative. In addition, starlike random copolymers of methyl methacrylate containing varying amounts of hydroxyethyl methacrylate with slightly higher polydispersities have been synthesized. Preliminary results show that these copolymers can be used to produce nanophase-separated inorganic/organic hybrids by templating vitrification of methylsilsesquioxane (MSSQ) and nanoporous thin films after subsequent thermal degradation of the organic polymer. Transmission electron microscopy confirms a nanoporous morphology of the thin films, and a decrease of the dielectric constant is observed.

Stamm, M. (1997). Grafting of polypeptides on solid substrates by initiation of N-carboxyanhydride polymerization by aminoterminated self-assembled monolayers. Langmuir, 13(4), 723-728. DOI: 10.1021/la960467g Copyright Other than for strictly personal use, it is not permitted to download or to forward/distribute the text or part of it without the consent of the author(s) and/or copyright holder(s), unless the work is under an open content license (like Creative Commons).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. Volker Erb and Manfred StammMax-Plank-Institut fü r Polymerforschung, Ackermannweg 10, 55128 Mainz, Germany Received May 13, 1996. In Final Form: December 9, 1996 A series of mixed self-assembled monolayers of functionalized (Br(CH2)11SiCl3) and unfunctionalized (CH3(CH2)10SiCl3) alkyltrichlorosilanes of different compositions have been prepared on bulk silicon substrates. By in situ modification of these monolayers the bromo end groups were transformed to amino end groups as shown by X-ray photoelectron spectroscopy measurements. The change of hydrophilicity was monitored by water contact angle measurements, showing the expected decrease of contact angles with increase amino group content on the surface. These substrates were used to initiate Ncarboxyanhydrides in dioxane to yield R-helical polypeptides grafted from the surface. The thicknesses of the obtained polymer layers were measured with ellipsometry and X-ray reflectometry. Fourier transform infrared measurements confirm that the grafted polymers are in the R-helical conformation.

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The synthesis of unique miktofunctional µ-initiators, combining initiator sites for both controlled ring-opening polymerization (ROP) and atom transfer radical polymerization (ATRP) arranged in an alternating fashion, is described. This initiator was used to prepare miktoarm star block copolymers in a core-out approach utilizing consecutive ATRP and ROP processes. NMR and GPC studies on the block copolymers comprising poly(methyl methacrylate) (PMMA) and poly(caprolactone) (PCL) confirm the versatility of this approach which is independent of the order of polymerization. Furthermore, amphiphilic alternating arm block copolymers containing poly(caprolactone) and poly(acrylic acid) blocks were also prepared by this method.

The chemoenzymatic cascade synthesis of block copolymers combining enzymatic ring opening polymerization (eROP) and atom transfer radical polymerization (ATRP) is reviewed. Factors like reaction condition and initiator structure were investigated and optimized prior to the polymerization. The synthesis of block copolymers was successful in two consecutive steps, i.e. eROP followed by ATRP as evident from SEC and GPEC analysis. While in the one-pot approach, block copolymers could be obtained by sequential addition of the ATRP catalyst, side reactions were observed when all components were present from the start of the reaction. A successful one-pot synthesis was achieved by conducting the reaction in supercritical carbon dioxide. 216

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