production of selected secondary metabolites in transformed ...

More documents

Recommendations

Info

eflux condenser equipped with bubble flask filled with silicon oil. Then 55μL of Karstedt catalyst solution in xylene (3 wt.%, 3,64 μmol) was injected to the reaction flask and the mixture was heated in 80 °C oil bath under reflux for 24 hours. THF was evaporated and the product POSS-Br was vacuum dried. R R R Si O O Si O O Si O R Si O O R O Si Si O O Si O O Si R H C H 3 R + C H 2 RH3 = C O O CH 3 Br CH 3 Karstedtův Karstedt's katalyzátor catalysator catalyst THF, reflux 24 hours Fig. 3: Synthesis of POSS-Br initiator Polymerizations Polymerization 1: A typical polymerization is as follows: 31 mg CuBr was placed into a 50 mL double-neck flask; the flask was evacuated and filled with nitrogen. Under a nitrogen blanket 5 mL of styrene, 40 μL of PMDETA and 4.6 g of p-dimethoxybenzene was added. The mixture was stirred until a homogenous solution formed and was placed into a 120°C oil bath under nitrogen. After heating to the reaction temperature 0,48 g of POSS-Br (initiator) was added. The solution turned dark green as the reaction began. Periodically, small amounts of reaction mixture were removed for kinetic and molecular weight analysis (conversion was determinated by weight analysis, molecular weight of polymers was determined using gel permeation chromatography). Molar ratios: Styrene:POSS-Br:CuBr:PMDETA - 100:1:0.5:0.5. Polymerization 2: This polymerization is similar to the polymerization 1, except the POSS-Br initiator is replaced with 65 μL of ethyl-α-bromo-isobutyrate, which was injected to the hot mixture via rubber septum. Molar ratios: Styrene:EBIB:CuBr:PMDETA - 100:1:0.5:0.5. RESULTS Reason for using POSS as an initiator of ATRP is to get a polystyrene macromolecule with one bulky POSS group at one of the chain ends; the initiator of ATRP remains the inseparable part of the macromolecule. Molecular weight plots prove living character of polymerizations; molecular weight grows linearly with conversion, with conversion growing to almost 100%. Linear dependence of conversion on time in semi logarithmic coordinates (Fig. 5) shows the first-order kinetic with respect to monomer. From the molecular weight plot of polymerization 1 (Fig. 6) it is obvious, that initiation efficiency is low and only about one half of the POSS initiator molecules is used for initiation; this causes the molecular weight to be twice as high as is should be according to the theoretical value determined from molar ratio monomer:initiator. In contrast, polymerization 2 initiated with low molecular weight initiator EBIB behaves in accordance with theory (Fig. 7). R R O Si O R Si O O Si O R Si O Sborník soutěže Studentské tvůrčí činnosti Student 2006 a doktorské soutěže O cenu děkana 2005 a 2006 Sekce DSP 2006, strana 230 O Si O O Si R R O O Si Si O R O O CH 3 Br CH 3
Differences can be caused by several reasons; no one of these reasons was studied in this work in detail, so the following ideas must be taken as a speculations. One factor could be different solubility of catalyst system due to the presence of different initiator in reaction mixture; it is also important to rule out the possibility of conventional free radical polymerization taking place to form polystyrene homopolymer, although the catalyst system should inhibit this reaction; part of POSS based initiator molecules could be deactivated with some side reaction, or there is just a steric block for approach of molecules of catalyst or monomer to the bulky POSS molecule; these ideas must be taken into consideration in subsequent work on this project. Convers ion [%] ln([M]0/[M]t) M 100 2 1 80 60 40 20 0 0 200 400 600 800 1000 t [min] Fig. 4: Kinetic plots 0 0 100 200 300 400 500 25000 20000 15000 10000 5000 t [min] Fig. 5: Semilogarithmic kinetic plots 0 1.00 0 20 40 60 80 100 Co nve rs io n [%] 1.70 1.60 1.50 1.40 1.30 1.20 1.10 D Polymerization 1 Polymerization 2 Polymerization 1 Polymerization 2 M(th e o r.) Fig. 6: Molecular weight plot for polymerization 1 Sborník soutěže Studentské tvůrčí činnosti Student 2006 a doktorské soutěže O cenu děkana 2005 a 2006 Sekce DSP 2006, strana 231 M D
Page 1 and 2: PRODUCTION OF SELECTED SECONDARY ME
Page 3 and 4: containing ampicillin, IPTG and x-g
Page 5 and 6: THE SIMPLE METHOD FOR THE RECOGNITI
Page 7 and 8: Figure 1 Negative-ion mode MALDI-TO
Page 9 and 10: Table 1 Evaluation of negative-ion
Page 11 and 12: Fig. 1: Scheme of the hydride gener
Page 13 and 14: [4] H. Matusiewicz, M. Kopras, J. A
Page 15 and 16: - are hypotriglyceridemic; - exhibi
Page 17 and 18: HYDROPHOBIZED SODIUM HYALURONATE IN
Page 19 and 20: spectrophotometer (AMINCO-Bowman, S
Page 21 and 22: Hyaluronate derivatives showed with
Page 23 and 24: copolymers were additionally functi
Page 25 and 26: Each micelle has a hydrophobic core
Page 27 and 28: STUDY OF THE COPPER(II) IONS NON-ST
Page 29 and 30: CuSO4, Cu(ClO4)2 and Cu2P2O7 of the
Page 31 and 32: total flux [mol.m -2 ] 0.7 0.65 0.6
Page 33: number of free radicals is very low
Page 37 and 38: MEASUREMENT OF THERMOPHYSICAL PROPE
Page 39 and 40: The typical time responses of tempe
Page 41 and 42: Figure 4 illustrates the typical de
Page 43 and 44: sodium sulphate and filtered to a 5
Page 45 and 46: Compare all tested evening primrose
Page 47 and 48: IMPROVED FLUORIMETRIC DETERMINATION
Page 49 and 50: Al F i 80 70 60 50 40 30 20 10 0 0
Page 51 and 52: F i 60 50 40 30 20 10 Data UCL LCL
Page 53 and 54: PHYSICAL-CHEMICAL ASPECTS OF PAINT
Page 55 and 56: Finally, the solubility parameter o
Page 57 and 58: Study of the influence of different
Page 59 and 60: Fig.1: Chemical structures of pI ma
Page 61 and 62: Identification of pI markers - Firs

production of selected secondary metabolites in transformed ...

Create successful ePaper yourself

Delete template?

Save as template?