Search results for "Mono"
showing 10 items of 6843 documents
α,ω-Functionalized poly-N-isopropylacrylamides: controlling the surface activity for vesicle adsorption by temperature
2003
The synthesis of alpha,omega-end-functionalized copolymers of N-isopropylacrylamide and N-(3-dimethylaminopropyl)acrylamide was performed. Monomer ratios of 100:0, 96:4, and 81:19 were investigated. The lower critical solution temperature (LCST) of these polymers was determined by cloud-point measurements and by microcalorimetric measurements. The LCST increased from 32 over 37 to 47 degrees C as the hydrophobicity increased with increasing amount of comonomer N-(3-dimethylaminopropyl)acrylamide. The polymers could successfully be adsorbed onto gold surfaces. Finally, vesicle adsorption onto these self-assembled polymer films on flat gold surfaces was investigated as the vesicle solution te…
High-Performance Electron-Transporting Polymers Derived from a Heteroaryl Bis(trifluoroborate)
2011
In this communication, we report that dipotassium aryl bis(trifluoroborate)s make stable and easy-to-purify yet reactive monomers under Suzuki polycondensation reactions. A bis(trifluoroborate) of 2-alkylbenzotriazole was prepared successfully and copolymerized with dibromobenzothiadiazole in the presence of a Pd catalyst and LiOH, yielding high molecular weight conjugated polymers. This polymer (P1) composed of all electron-accepting units shows excellent electron-transport properties (μ(e) = 0.02 cm(2) V(-1) s(-1)), which proves the value of the aryl bis(trifluoroborate) monomers and suggests that many other types of semiconducting polymers that could not be accessed previously can be syn…
Rigid biobased polycarbonates with good processability based on a spirocyclic diol derived from citric acid
2020
Introducing biobased polymers from renewable sources for use as high-performance thermoplastics with high demands on mechanical rigidity, transparency, thermal stability, as well as good processability, is a significant challenge. In the present work we have designed and prepared a rigid biobased bis-spirocylic diol by di-cycloketalization of a bicyclic diketone (cis-bicyclo[3.3.0]octane-3,7-dione, obtained from citric acid) using trimethylolpropane. This spiro-diol monomer has two reactive primary hydroxyl groups and the synthesis from inexpensive biobased starting materials is straightforward and readily upscalable, involving no chromatographic purification. In order to explore the useful…
Molecular Parameters of Hyperbranched Polymers Made by Self-Condensing Vinyl Polymerization. 2. Degree of Branching
1997
Using a modified definition, the average degree of branching, , the fraction of branchpoints, , as well as the fractions of various structural units are calculated as a function of conversion of double bonds for hyperbranched polymers formed by self-condensing vinyl polymerization (SCVP) of monomers (or “inimers”) with the general structure AB*, where A is a vinyl group and B* is an initiating group. The results are compared to those for the polycondensation of AB2-type monomers. At full conversion, is somewhat smaller for SCVP ( ∞ ≈ 0.465) than for AB2 systems ( ∞ = 0.5). There are two kinds of linear groups in SCVP whereas there is only one kind in AB2 systems. Since there are two differe…
Effect of core-forming molecules on molecular weight distribution and degree of branching in the synthesis of hyperbranched polymers
1998
The polydispersity index, the molecular weight distribution (MWD), and the degree of branching ( ) are calculated for hyperbranched polymers obtained in self-condensing vinyl polymerization of AB* monomers in the presence of a core-forming molecule (i.e. a multifunctional initiator, Bf*). Two cases are considered: (a) batch polymerization, i.e., with all components mixed together; (b) semibatch polymerization, i.e., slow addition of the monomer to the core-forming molecule. The results obtained for the latter case are also valid for polycondensation of AB2 monomers. The presence of core-forming molecules leads to a considerable narrowing of the MWD's, the polydispersity index decreasing wi…
Synthesis of Defined Poly(silsesquioxane)s: Fast Polycondensation of Trialkoxysilanes in a Continuous-Flow Microreactor
2009
The polycondensation of trialkoxysilanes to PSSQs in a microreactor setup is demonstrated. While continuous-flow processes involving microreactors found various applications in chain growth polymerization, their influence on step-growth polymerization is less explored, and the polycondensation of multifunctional monomers has not been studied in detail. We found significantly increased yields and a decreased polydispersity of the obtained polymers in comparison to the batch process. By variation of the residence time molecular weights could be adjusted reproducibly ranging from M n =1900 to 11000 g · mol -1 . Thus, the microreactor setup offers for the first time the possibility to synthesiz…
New ferrocene-containing copolyesters
1995
We have synthesized four new ferrocene monomers (three diols and one diester). The redox potential of these ferrocene derivatives varies between 0 mV and 230 mV due to different degrees of ring alkylation. Amorphous and liquid crystalline copolyesters were prepared with these monomers in the polymer main chain. Cyclovoltammetric measurements show that the redox potential of the ferrocene units is increased by about 40 mV upon polymer formation (esterification). Since the ester group is 4 to 6 σ-bonds away from the ferrocene unit this increase is probably caused by some charge-transfer interaction through space. First rheological measurements show an unusual rubber-like behaviour of the ferr…
Synthesis of Oxetane-Functional Aliphatic Polyesters via Enzymatic Polycondensation
2012
Synthesis, characterization, and thermal properties of a series of oxetane-functional aliphatic polyesters are investigated. The incorporation of the acid-sensitive 3,3-bis(hydroxymethyl)oxetane (BHMO) into polymers is achieved by using the enzyme CALB (Candida antarctica Lipase B) as a catalyst. This mild synthetic strategy provides well-defined, oxetane-functional polyesters. The enzymatic polycondensation allows for the synthesis of a series of aliphatic polyesters containing various ratios of the difunctional monomers sebacic acid, 1,8-octanediol, and BHMO with molecular weights between 5000–9800 g mol−1 and polydispersity indices (Mw/Mn) in the range of 1.25 and 1.92. Furthermore, cros…
Synthesis of new electroactive polymers by ion-exchange replacement of Mg(II) by 2H+ or Zn(II) cations inside Mg(II) polyporphine film, with their su…
2014
Abstract It has been demonstrated that the treatment of the magnesium polyporphine of type I, pMgP-I, by trifluoroacetic acid in acetonitrile may be used to replace initial central Mg(II) cations inside the monomeric macrocycle units by protons, to get a new electroactive polymer, “free-base polyporphine of type I”, pH2P-I. In its turn, these inserted protons may be replaced by Zn(II) cations via the film treatment with zinc acetate in organic solvent, to get another new electroactive polymer, “zinc polyporphine of type I”, pZnP-I. These changes of central ions inside monomer units manifest themselves by characteristic modifications of their electroactive properties as well as of UV–visible…
Light-induced demixing of hole or electron transporting moieties
2004
This paper describes the synthesis of two tri-phenylamine monomers (hole conducting) and one triazine monomer (electron conducting) which differ in their copolymerization parameters because of their styrene and vinyl ester nature. A blend of triphenylamine monomer and poly-(ethylene glycol) and mixtures of both types of monomers (triphepylamine and triazine) were illuminated through a line mask, creating laterally modulated radicals, thus leading to lateral demixing. The experiments with mixtures of triphenylamine and triazine monomers show that the concentration of p- or n-type polymers can be modulated laterally in a controlled way.