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41.
Georgios Floros Fotini Agrafioti Alexios Grigoropoulos Patrina Paraskevopoulou Konstantinos Mertis Maria Tseklima Maria Veli Marinos Pitsikalis 《Journal of polymer science. Part A, Polymer chemistry》2013,51(22):4835-4844
Statistical copolymers of norbornene (NBE) with 5‐vinyl‐2‐norbornene (VNBE) were prepared by ring‐opening metathesis polymerization, employing the triply bonded ditungsten complex Na[W2(μ‐Cl)3Cl4(THF)2].(THF)3. NMR measurements revealed that the side vinyl groups of the VNBE monomer remain intact during the copolymerization reaction. The reactivity ratios were estimated using the Finemann–Ross (FR), the inverted FR, and the Kelen–Tüdos graphical methods. Structural parameters of the copolymers were obtained by calculating the dyad sequence fractions, which were derived using the monomer reactivity ratios. The glass transition temperatures, Tg, of the copolymers were measured by differential scanning calorimetry measurements and were examined in the frame of several theoretical equations allowing the prediction of these Tg values. The best fit was obtained using methods that take into account the monomer sequence distribution of the copolymers. Finally, the kinetics of the thermal decomposition of the copolymers was studied by thermogravimetric analysis in the frame of the Ozawa–Flynn–Wall and Kissinger methods. © 2013 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2013 , 51, 4835–4844 相似文献
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Dimitrios Priftis Marinos Pitsikalis Nikos Hadjichristidis 《Journal of polymer science. Part A, Polymer chemistry》2007,45(22):5164-5181
A novel heterofunctional initiator, synthesized from pentaerythritol in a three step reaction sequence with two ring opening polymerization (ROP) and two atom transfer radical polymerization (ATRP) initiating sites, was used to prepare A2B2 miktoarm star copolymers of poly(ε‐caprolactone), PεCL, with polystyrene, PS, poly(methyl methacrylate), PMMA, poly(dimethylaminoethyl methacrylate), PDMAEMA, and poly(2‐hydroxyethyl methacrylate), PHEMA. A2B miktoarm stars, A being PεCL or poly(δ‐valerolactone), PδVL and B PS were also prepared from ω,ω‐dihydroxy‐PS, synthesized from ω‐Br‐PS and serinol, by ROP of εCL or δVL. All polymers were characterized by size exclusion chromatography, 1H NMR spectroscopy, and membrane osmometry. © 2007 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 45: 5164–5181, 2007 相似文献
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Ioannis Choinopoulos Spyros Koinis Marinos Pitsikalis 《Journal of polymer science. Part A, Polymer chemistry》2017,55(6):1102-1112
We report the synthesis of the novel half‐titanocene alkoxide complex bischloro‐η5‐cyclopentadienyl(bicyclo[2.2.1]‐hept‐5‐en‐2‐oxy) titanium (IV), [CpTiCl2(O‐NBE)]. This complex was employed for the synthesis of chiral poly(l ‐lactide‐b‐hexyl isocyanate) diblock copolymer bearing a norbornene end group with sequential addition of monomers. The poly(hexyl isocyanate) block is chiral due to the last l ‐lactide unit of the poly(l ‐lactide) block. This macromonomer was polymerized towards a chiral polymer brush structure with polynorbornene backbone and chiral poly(l ‐lactide‐b‐hexyl isocyanate) side chains using Grubbs first‐generation catalyst. The polymers were characterized using size exclusion chromatography (SEC), nuclear magnetic resonance (NMR), and circular dichroism (CD) spectroscopy and their thermal properties were investigated by thermogravimetric analysis (TGA) and differential scanning calorimetry (DSC) analysis. © 2017 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2017 , 55, 1102–1112 相似文献
45.
Andreas Marinos 《International Journal of Mathematical Education in Science & Technology》2013,44(5):625-648
In this work, an attempt is made to evaluate the errors that have to do with the interpretation and construction of graphic representations. Although the students are studying in the second year of technical high school (secondary education), i.e. in schools with an emphasis in technical subjects (post junior secondary), it is observed that they find difficult to handle the graphic representations. This is an attempt to overcome the difficulties that exist by putting the students to work on electrical machines. They read, construct or verify the graphic representations of the electrical machines using electrical instruments with which they carry out measurements and take values. It is evaluated after the end of each activity and also after a suitable interval of time that there is an improvement in the students’ abilities (interpretation and construction) in graphic representations. 相似文献
46.
Statistical copolymers of 2-vinylpyridine (VP) with oligo(ethylene glycol) methyl ether methacrylates of two different molecular weights (300 g/mol (OEGMA300) and 1100 g/mol (OEGMA1100)), were prepared by free radical polymerization. The reactivity ratios of these two sets of monomers were estimated using the Finemann–Ross, the inverted Finemann–Ross and the Kelen–Tüdos graphical methods. Structural parameters of the copolymers were obtained by calculating the dyad monomer sequence fractions and the mean sequence length. The effect of the length of the oligo(ethylene glycol) group on the copolymer structure is discussed. The glass-transition temperature (Tg) values of the VP copolymers with OEGMA300 were measured and examined in the frame of several theoretical equations, allowing the prediction of these Tg values. The copolymers of VP with OEGMA1100 exhibited the characteristic melting endotherm, due to the crystallinity of the methacrylate sequences and glass transition temperatures attributed to the PVP sequences. 相似文献
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Nikos Hadjichristidis Marinos Pitsikalis Hermis Iatrou Stergios Pispas 《Macromolecular rapid communications》2003,24(17):979-1013
The efficiency of the macromonomer (MM) synthetic strategy for the creation of nonlinear complex macromolecular architectures (miktoarm stars, α,ω‐branched polymers, random/exact comb and graft copolymers, dendritic polymers, molecular brushes) is reviewed. In addition, the solution/bulk properties and the potential applications of polymacromonomers (PMM), as well as new synthetic ideas are presented. The synthesis of macromonomers and living polymacromonomers in situ leads to many novel linear and nonlinear structures, as for example PMM‐b‐PS‐b‐PMM, (PS)2PMM. The use of multichlorosilylstyrenes as monomer/linking agents opens new ways for structures with multichain macromonomeric building blocks.