Highly branched poly(ε-caprolactones) with novel and well-defined molecular architectures have been synthesized by the use of new multifunctional initiators. The ring-opening polymerization methods used to prepare these new structures allowed accurate control of molecular weight and narrow molecular weight distributions. In addition, the synthesis of even more complex molecular architectures was possible by the use of 1,4,9-trioxaspiro[4.6]-9-undecanone as a comonomer with ε-caprolactone. After copolymerization, complete deacetalization of the polyester chains into the corresponding ketone groups followed by quantitative reduction formed polymers with hydroxyl pendant groups. With this synthetic strategy, significant additional functionality was introduced. In addition, the pendant hydroxyl groups along the chains can serve as macroinitiators for the further initiation of ε-caprolactone to prepare dendri-graft molecular architectures. The new polymers were characterized by 1H NMR, 13C NMR, and size exclusion chromatography (SEC). 13C NMR spectra clearly showed that the hydroxyl groups of the initiators were fully substituted to give polymers with two, four, and six arms.

Dendronized, hybrid dendritic−linear polymers were synthesized by either the “graft-onto” route or by atom transfer radical polymerization (ATRP) of macromonomers. In both ways, the main chain was composed of acrylate repeating units and the dendrons were based on the aliphatic ester skeleton obtained from 2,2-bis(methylol)propionic acid (bis-MPA). ATRP of macromonomers was not a viable route for monomers with side chains larger than second-generation dendrons, which is why a combination of the two approaches was required to obtain polymers with larger side chains. The “graft-onto” route was conducted by reacting hydroxyl groups on the main chain with the acetonide-protected 2,2-bis(hydroxymethyl)propionic anhydride. The acetonide protecting group was easily removed by treating a solution of the polymer with an acidic ion-exchange resin. Dendronized polymers with 1−3 generation dendron side groups were synthesized with a maximum molecular weight of ca. 86 kDa. The products were analyzed by 1H and 13C NMR, SEC, and MALDI−TOF.

Novel syntheses of bifunctional liquid-crystalline acrylate and methacrylate monomers are described. Thermal and microstructural characterization of the monomers using small-angle X-ray scattering, differential scanning calorimetry, and optical microscopy revealed the presence of smectic A, smectic C, and smectic E phases. Photopolymerization of the bifunctional monomers conducted at different temperatures preserved the monomeric liquid-crystalline structure in the cross-linked polymers. The densely cross-linked polymers showed thermal reversibility. Mixtures of these monomers and chiral monofunctional liquid-crystalline monomers exhibited chiral smectic C mesomorphism that was permanented by photopolymerization and subsequent cross-linking.

During the last few years, new developments in polymer photochemistry have made it possible to graft various functional monomers onto surfaces of inert polymers like polyethylene, polypropy lene and polyethyleneterephthalate. In the first attempts, initiator and monomer were transferred in vapor phase into a "UV Cure" irradiator con taining the polymer sheet to be surface grafted. After a few minutes irradiation with a high pressure mercury lamp at about 50°C, a rather complete cover of grafted acrylic acid, acrylamide and other vinyl monomers could be obtained. In later experiments a continuous grafting method has been developed where a tape or a fiber bundle after suitable pretreatment is grafted by UV irra diation for a few seconds. Homopolymer formed is removed by washing and grafted polymer analyzed by dye absorption, IR reflection and ESCA spectro scopy.During the last 30 years radiation chemistry has been and still is an active area of polymer research. High energy radiation, e.g. electron beam and gamma radiation, initiates ionization and radical formation in polymers which may result in modification, crosslinking and/or degradation. An early studied and common modification involves ionizing irradiation followed by free radical initiated graft copoly merization of monomers present or subsequently added (1). Radiation induced free radical graft copolymerization has also been accomp lished using UV light (2). Since the pioneering work by Oster et al. in the 1950 ? s (3,4;) where monomers were photografted with UV light onto polymers blended with photoinitiators, only few researchers have more recently followed up this work. The interest has been focused on the use of high energy radiation. In a study in the 1960 T s by Howard et al. (_5) thin polymer films were saturated with monomers and then modified by irradiation with

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