Telechelic oligo- and poly(dimethylsiloxanes) 1 and 2, with two ureidopyrimidone (UPy) functional groups, have been prepared via a hydrosilylation reaction. The compounds have been characterized in solution by 1H NMR and viscometry and in the solid state by 1H NMR and 13C NMR, FTIR, and rheology measurements. The measurements show that the UPy groups of 1 and 2 are associated via quadruple hydrogen bonds in a donor−donor−acceptor−acceptor (DDAA) array. In many aspects, the materials behave like entangled, high molecular weight polymers. Compound 2 has a T g at −119 °C and shows melting of microcrystalline domains of associated UPy units at −25 °C. Compound 1 has a crystalline form (T m = 112 °C) and an amorphous modification with a T g of 25 °C. Solid-state NMR was used to investigate the mobility of these phases. WISE spectra show a higher mobility of the UPy groups in the amorphous phase than in the crystals of 1. Amorphous 1 and 2 behave like entangled polymers. Their mechanical behavior is characterized by a rubbery plateau and a relatively high activation enthalpy for stress relaxation (ΔH = 127 kJ/mol for 1; ΔH = 54 kJ/mol for 2), which was derived from the temperature dependence of the zero-shear viscosity. Estimates for the degree of polymerization (DP) of 1 and 2, based on the mechanical properties, give DP > 100 for 1 and approximately 20 for 2. Like in condensation polymerization, the DP's of reversible supramolecular polymers are presumably limited by the presence of small amounts of monofunctional impurities.

Block copolymers of lactide and poly(ethy1ene glycol) with various mclar ratios were synthesized. Tin(I1) bis(2-ethylhexanoate) has been used as a catalyst. Kinetic measurement and mechanistic studies suggest that the reactivity of the initiator, a hydroxyl group bearing reagent, is an important parameter on the polymerization course. In the case of primary and secondary alcohols, Le., poly(ethy1ene glycol) and methyl lactate, it is found that when the initiator concentration exceeds the catalyst concentration, the number of chains formed exceeds the number of catalyst molecules. The chains are propagated through shifts of catalysts from one chain to another. In the case of tertiary alcohols, it appears that the number of chains formed is about the number of catalyst molecules. Therefore, by choosing an appropriate initiator, reaction course and molecular weight as well as molecular weight distribution can be designed. A model based on the assumptions of fast initiation reaction and random propagation reaction is established. Both initiator and catalyst are found to have an influence on the increase of molecular weight and molecular weight distribution.

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DOI to the publisher's website. • The final author version and the galley proof are versions of the publication after peer review. • The final published version features the final layout of the paper including the volume, issue and page numbers. Link to publication General rights Copyright and moral rights for the publications made accessible in the public portal are retained by the authors and/or other copyright owners and it is a condition of accessing publications that users recognise and abide by the legal requirements associated with these rights. • Users may download and print one copy of any publication from the public portal for the purpose of private study or research. • You may not further distribute the material or use it for any profit-making activity or commercial gain • You may freely distribute the URL identifying the publication in the public portal. If the publication is distributed under the terms of Article 25fa of the Dutch Copyright Act, indicated by the "Taverne" license above, please follow below link for the End User Agreement:

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Low molar mass poly( 2,6-dimethyl-1 ,Cphenylene-ether)^ (PPE) have been prepared by the precipitation polymerization of 2,6-dimethylphenol (DMP ) under the action of a Cu( I )Cl/amine-catalyst and 02. The polymers prepared possess a rather narrow molecular weight distribution (D = 1.7-2.2), and the molecular weight can easily be controlled by adjusting the solvent mixture of 2-propanol and toluene. Molecular weights were determined using 'H-NMR spectroscopy, GPC, and FD-MS, and range from M, = 2700 to 7500 g/mol. No Mannich-basetype endgroups and no incorporation of DPQ (3,5,3',5'-tetramethyl-4,4 '-diphenoquinone) has been detected.

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New multiblock copolymers based on dimethylsiloxanes and phenylene diacrylate derivatives have been prepared by hydrosilation polymerization. Copolymerization was performed using either low molecular weight monomers or high molecular weight macromers. The organic macromer was prepared by acyclic diene metathesis (ADMET) polymerization of para‐phenylenediacrylic acid dipent‐4‐enyl ester. Hexamethyltrisiloxane and α,ω‐bishydride‐terminated polydimethylsiloxane (PDMS) were used as inorganic macromers. The copolymers show microphase separation of the soft siloxane block and the hard semicrystalline organic block, as observed by differential scanning calorimetry (DSC), X‐ray scattering experiments (SAXS and WAXS) and transmission electron microscopy (TEM). The crosslinking rate upon UV‐irradiation is slightly higher for the microphase‐separated copolymer than for the corresponding homopolymer. When films of the polyester‐PDMS multiblock copolymers were irradiated with linearly polarized light, optically anisotropic films were obtained with a polarizing efficiency of 67%, whereas the crosslinked films of the homopolymer had a polarizing efficiency of at most 43%.