Microporous organic polymers (MOP) of a new type have been synthesised in high yields by a simple coordination polymerization of 1,3-diethynylbenzene, 1,4-diethynylbenzene and 4,4'-diethynylbiphenyl catalysed by [Rh(cod)acac] and [Rh(nbd)acac] complexes. The new MOPs are non-swellable polyacetylene-type conjugated networks consisting of ethynylaryl-substituted polyene main chains that are crosslinked by arylene linkers. Prepared MOP samples have a mole fraction of branching units (by (13)C CP/MAS NMR) from 0.30 to 0.47 and exhibit the BET (Brunaer-Emmett-Teller) surface up to 809 m(2) g(-1) and hydrogen uptake up to 0.69 wt% (77 K, H2 pressure 750 torr).
The synthesis of mostly new acetylenes, R1CCR2, (R1 = 4‐t‐butylphenyl; R2 = 4‐t‐butylphenyl; 4‐[(t‐butyl)(diphenyl)silyloxy]phenyl; 1‐naphthyl; 2‐naphthyl; 9‐anthryl) is reported. Their UV‐vis characteristics are discussed in comparison to the results of TD‐DFT calculations. R1CCR2 (except for R2 = 9‐anthryl) give polyacetylenic polymers—[C(R1) = C(R2)]‐n, insoluble if R1 = R2 and well soluble if R1 ≠ R2 in polymerization with TaCl5/SnBu4. Polymerizability increases with increasing monomer triple bond accessibility for the catalyst. The photoluminescence yield of the soluble polymers rises in the R2 order: 1‐naphthyl < 2‐naphthyl < 4‐[(t‐butyl)(diphenyl)silyloxy]phenyl.
New stable polyacetylenes whose quantum yield of fl uorescence is increased up to 62% because of the presence of pendant 4-(piperidine-1-yl)-1,8-naphtalimide groups are described. The polymers are prepared by two-step modifi cation of copolymers of 1-(4-tert -butylphenyl)-6-chlorohex-1-yne and 1-phenylhex-1-yne consisting of the exchange of chlorine atoms at side groups for azide groups and subsequent Huisgen click reaction of the azide groups with ethynyl groups of N -(prop-1-yne-3-yl)-4-(piperidine-1-yl)-1,8-naphthalimide. Modifi cation is evidenced by 1 H NMR, IR, Raman and UV-vis spectroscopy. Modifi ed polymers show the excitation energy transfer from their main chains on fl uorophores and nearly preservation of fl uorescence properties of fl uorophores upon their binding to polymer chains.
Antifouling polymer layers containing extracellular matrix-derived peptide motifs offer promising new options for biomimetic surface engineering. In this contribution, we report the design of antifouling vascular grafts bearing biofunctional peptide motifs for tissue regeneration applications based on hierarchical polymer brushes. Hierarchical diblock poly(methyl ether oligo(ethylene glycol) methacrylate-block-glycidyl methacrylate) brushes bearing azide groups (poly(MeOEGMA-block-GMA-N3)) were grown by surface-initiated atom transfer radical polymerization (SI-ATRP) and functionalized with biomimetic RGD peptide sequences. Varying the conditions of copper-catalyzed alkyne-azide “click” reaction allowed for the immobilization of RGD peptides in a wide surface concentration range. The synthesized hierarchical polymer brushes bearing peptide motifs were characterized in detail using various surface sensitive physicochemical methods. The hierarchical brushes presenting the RGD sequences provided excellent cell adhesion properties and at the same time remained resistant to fouling from blood plasma. The synthesis of anti-fouling hierarchical brushes bearing 1.2 × 103 nmol/cm2 RGD biomimetic sequences has been adapted for the surface modification of commercially available grafts of woven polyethylene terephthalate (PET) fibers. The fiber mesh was endowed with polymerization initiator groups via aminolysis and acylation reactions optimized for the material. The obtained bioactive antifouling vascular grafts promoted the specific adhesion and growth of endothelial cells, thus providing a potential avenue for endothelialization of artificial conduits.
Polymer
brush coatings are effective in preventing blood coagulation
or bacterial attachment, but their chain conformation, while vital
for this effect, was never characterized in high spatial resolution.
Here, we report mid-infrared spectroscopic nanoscopy studies of few-nanometer-thin
poly(ethylene oxide) (PEO) films which reveal marked spectral variations
along the surface at a length scale smaller than 100 nm and originating
only from the physical conformation of the chains. The conformation
and average orientation of the polymer chains in the layer is extracted
from the spectra with the aid of theoretic modeling, confirming the
spontaneous formation of a crystalline phase. This result suggests
spectroscopic nanoscopy as a powerful new tool to characterize polymer
brush coatings.
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