Amine-functional poly(ethylene glycol)
(PEG) copolymers have been
prepared that exhibit thermo- and pH- responsive behavior in aqueous
solution. Three novel tertiary di(n-alkyl)glycidylamine
monomers have been introduced for anionic ring-opening copolymerization
(AROcP) with ethylene oxide (EO): N,N-di(n-butyl)glycidylamine (DButGA), N,N-di(n-hexyl)glycidylamine (DHexGA),
and N,N-di(n-octyl)glycidylamine
(DOctGA). Via controlled AROcP we synthesized well-defined (M
w/M
n = 1.05–1.14),
water-soluble block- and gradient-type PEG copolymers, containing
up to 25 mol % of the respective dialkylglycidylamine comonomer. Molecular
weights ranged from 4900 to 12 000 g mol–1. Detailed in-situ 1H NMR kinetics and 13C
triad analyses elucidate the microstructures of the copolymers and
the relative reactivity of the novel comonomers. Notably, the n-alkyl chain length had no significant influence on the
relative reactivity of the glycidylamine comonomers. Calculated reactivity
ratios ranged from r
EO = 1.84, r
DButGA = 0.49 to r
EO = 1.78, r
DOctGA = 0.42, manifesting
the formation of gradient copolymers. Thermo- and pH-responsive properties
of these copolymers are precisely tunable by the comonomer ratio,
and cloud points in aqueous solution can be adjusted between 21 and
93 °C. Electron paramagnetic resonance (EPR) spectroscopic studies
with TEMPO as a spin probe were conducted to elucidate host–guest
interactions of the copolymers. Unexpectedly, the n-alkyl chain length of the different glycidylamine comonomers only
influences the inverse phase transition of the gradient copolymers,
but not of the block copolymers on the nanoscale. Self-assembly of
the block- and gradient-type copolymers in aqueous alkaline solution
by both static and dynamic light scattering has also been investigated
after confirming the existence of pure unimers in methanol.
Hybrid conjugated polymers containing carborane directly bonded in the aromatic backbone repeat structure have interesting electronic bonding structures and are potentially useful new materials in organic electronics. Conjugated polymers based on o-carborane are particularly interesting for applications in sensing and detection because of the cage's unique bonding scheme and its bent geometry. Poly(fluorene) containing o-carborane displays multiple emission pathways that can be modulated through interactions with small molecules. In this paper, we report that films of poly(fluorene) with o-carborane in the backbone function as vapochromatic photoluminescent sensors toward volatile organic molecules.
The synthesis of diblock as well as gradient copolymers of N,N-diethyl glycidyl amine (DEGA) with ethylene oxide (EO) via anionic ring-opening polymerization is presented. The polymers exhibit low polydispersities (≤1.13) and molecular weights in the range of 3300-10 200 g mol(-1) . In PEG-co-PDEGA copolymers, incorporation of 4%-29% DEGA results in tailorable cloud point temperatures in aqueous solution and melting points depending on DEGA content. mPEG-b-PDEGA block copolymers can be quaternized to generate cationic double-hydrophilic polyelectrolyte copolymers with polyether backbone. Furthermore, mPEG-b-PDEGA has been used as dual reducing and capping agent for gold nanoparticle synthesis.
Detailed understanding of the monomer sequence distribution in carbanionic copolymerization was achieved by direct online monitoring of copolymerizations in an NMR tube. Obtaining detailed knowledge of the changing monomer concentration in stock during the reaction, this technique permits to determine the incorporation probability for each monomer at every position of the polymer chain. An in situ kinetic study of two different carbanionic copolymerizations has been carried out. On the one hand, the copolymerization of the structurally similar, protected hydroxystyrene derivatives, p-(1-ethoxy ethoxy)styrene (pEES) and 4-tert-butoxystyrene (tBuOS), and on the other hand the copolymerization of the chemically different monomers, styrene (S) and pEES, have been studied. Whereas in the first case a slight deviation from an ideal random copolymerization was observed, the latter copolymerization leads to gradient copolymers. Real-time 1 H NMR spectroscopy gave detailed insight into the reaction behavior at every stage of the copolymerization and leads to precise understanding of the resulting gradient structures.
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