The Convenient Synthesis of Hydrogen‐Bonded Ureidopyrimidinones

Keizer, Henk M.; Sijbesma, Rint P.; Meijer, E. W.

doi:10.1002/ejoc.200300752

Cited by 65 publications

(70 citation statements)

References 22 publications

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“…N,NDimethylformamide (DMF) was dried over 4 Å molecular sieves. tert-Butyl 6-hydroxyhexylcarbamate was prepared as reported by Forbes et al 51 Tris[2-(dimethylamino)ethyl]amine (Me 6 TREN) was prepared as reported by Queffelec et al 52 2-(1-Imidazolylcarbonylamino)-6-methyl-4-[1H]-pyrimidinone was prepared as reported by Keizer et al 53 Ethane-1,2-diyl bis(2-bromo-2-methylpropanoate) was synthesized as reported by Matyjaszewski et al 54 n-Butyl acrylate was purified by passing over neutral alumina. Acryloyl chloride was distilled prior to use.…”

Section: Methodsmentioning

confidence: 99%

Model Transient Networks from Strongly Hydrogen-Bonded Polymers

Feldman¹,

Kade²,

Meijer³

et al. 2010

Macromolecules

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Random copolymers consisting of n-butyl acrylate backbones with quadruple hydrogenbonding side chains based on 2-ureido-4[1H]-pyrimidinone (UPy) have been synthesized via controlled radical polymerization and postpolymerization functionalization. Through this synthetic strategy high UPy monomer content (15 mol %) can be reached while maintaining low polydispersity and excellent control over molecular weight, providing model reversible networks with well-defined molecular architecture. Despite low T g s and a lack of entanglements or crystallinity, these materials behave as thermoplastic elastomers through the strong but reversible association of UPy groups. Bulk properties such as the plateau modulus, tensile modulus, and relaxation time scale are primarily determined by the average distance between UPy's along the chain. Starting from a difunctional initiator, triblock copolymers can also be synthesized containing a homopolymer midblock and random copolymer end blocks, effectively concentrating the hydrogen-bonding groups near the chain ends. By controlling both the average composition and distribution of UPy's along the polymer chain, macroscopic material properties such as stiffness and resistance to creep can be independently tuned.

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Section: Methodsmentioning

confidence: 99%

Model Transient Networks from Strongly Hydrogen-Bonded Polymers

Feldman¹,

Kade²,

Meijer³

et al. 2010

Macromolecules

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“…[35][36][37] UPy-based supramolecular polymeric materials prepared from telechelic polymers by functionalization with UPy synthons 18,25,27,38,39 are promising candidates for applications. The rheology of the melt state of such UPy-telechelic polymers is more complex 40,41 than for unidirectionally associated telechelic monomers or for the coordinatively cross-linked polymer networks described by Craig [42][43][44] and co-workers.…”

Section: Introductionmentioning

confidence: 99%

Unidirectional Dimerization and Stacking of Ureidopyrimidinone End Groups in Polycaprolactone Supramolecular Polymers

et al. 2007

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The effect of stacking of end groups on the rheological behavior of supramolecular polymer melts is reported. Oscillatory shear experiments in the transition zone from the pseudo rubber plateau to the flow region of telechelic polycaprolactones (PCLs) with ureidopyrimidinone (UPy) end groups directly attached to PCL can be fitted with a single Maxwell element. This demonstrates that dimerization of the UPy groups is unidirectional and that reversible chain scission is faster than reptation. If the UPy groups are connected to the polymer via a urethane linker, a low-frequency plateau in G′ is observed. This is ascribed to the formation of a network of stacked UPy dimers, aided by urethane hydrogen bonding. Below their melting point, these stacks form long fibers in the urethane linked supramolecular poly(methyl caprolactone), which were observed with atomic force microscopy (AFM). Steric hindrance interferes with stacking, since the plateau in G′ is lower in a urethane linked polymer with bulky adamantyl-UPy end groups.

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“…Aer deprotection, an increase in the apparent molecular weight is observed to M n ¼ 18.1 kDa, PDI ¼ 1. 24. The lower molecular weight observed in CHCl 3 compared to THF before deprotection could indicate that P5a has more interactions with the column, which results in an increase in the retention time.…”

mentioning

confidence: 98%

The balance between intramolecular hydrogen bonding, polymer solubility and rigidity in single-chain polymeric nanoparticles

et al. 2013

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A library of copolymers with pendant, protected ureido-pyrimidinone (UPy) groups was prepared applying controlled polymerization techniques. The polymer backbones were based on polyacrylate, polymethacrylate, polystyrene and polynorbornene and differ in stiffness, molecular weight and the linking moiety between the backbone and the UPy group. In all cases, the percentage of protected UPy groups was kept constant. The effect of solvent on the behaviour of the polymers before and after removal of the protecting groups was evaluated in, among others, chloroform and tetrahydrofuran (THF).After deprotection of the UPy protecting group, the UPys dimerize via four-fold H-bonding in THF, inducing a collapse into single-chain polymeric nanoparticles (SCPNs), as evidenced by a combination of 1 H-NMR spectroscopy, size-exclusion chromatography and dynamic light scattering. In chloroform, on the other hand, dimerization of the UPy groups is present but interchain interactions occur as well, resulting in less-defined SCPNs. Remarkably, the flexibility of the polymer backbone, the polymer molecular weight and the nature of the linker unit all do not affect SCPN formation. In contrast, the interaction between solvent and the UPy moiety is a critical parameter for SCPN formation. For example, strong intramolecular dimerization of the UPys is observed in THF while interparticle interactions are suppressed. From this investigation we conclude that a wide variety of polymer backbones are suitable for polymer collapse via supramolecular interactions and thus allow for the formation of SCPNs but that the solvent choice is crucial to enhance intramolecular H-bonding and, at the same time, to suppress interparticle interactions.

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The Convenient Synthesis of Hydrogen‐Bonded Ureidopyrimidinones

Cited by 65 publications

References 22 publications

Model Transient Networks from Strongly Hydrogen-Bonded Polymers

Model Transient Networks from Strongly Hydrogen-Bonded Polymers

Unidirectional Dimerization and Stacking of Ureidopyrimidinone End Groups in Polycaprolactone Supramolecular Polymers

The balance between intramolecular hydrogen bonding, polymer solubility and rigidity in single-chain polymeric nanoparticles

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