Fluoropolyethers end‐capped by polar functional groups. I. Kinetic approach to the reaction of hydroxy‐terminated fluoropolyethers with cycloalyphatic and aromatic diisocyanates

Mashlyakovskiy, Leonid; Zaiviy, Vladimir; Simeone, Giovanni; Tonelli, Claudio

doi:10.1002/(sici)1099-0518(19990301)37:5<557::aid-pola6>3.3.co;2-9

Cited by 4 publications

(20 citation statements)

References 0 publications

Supporting

Mentioning

Contrasting

Order By: Relevance

“…CHI (Aldrich) and DBTDL (MαT Chemicals, Inc.) were used without further purification. The solvents EA, HFX, tetrahydrofuran (THF), and MIBK (Aldrich) were purified as described previously 1…”

Section: Methodsmentioning

confidence: 99%

“…The procedure used for the kinetic measurements by an IR method is described in a previous article 1. We checked the reaction by following the decrease in the intensity of the NCO absorption band at 2268 cm −1 .…”

Section: Methodsmentioning

confidence: 99%

“…To better understand the behavior of FPEs of various molecular weight and structures, we have studied the kinetics of some model reactions. These include the tin‐catalyzed reactions of cyclohexyl isocyanate (CHI) at NCO:OH = 1 with (1) FPE diol (Z‐DOL H‐1000) of the structure and (2) monofunctional alcohols of different molecular weights, such as trifluoroethanol (TFE) and some 2‐substituted TFEs, GAL 7002X, GAL‐402, and CF 3 ‐Z‐DOL‐OH, which has a structure similar to that of Z‐DOL: Unlike in our previous works,1, 2 in which isophorone diisocyanate (IPDI), with two NCO groups of different reactivities,3–9 was studied, in this study CHI was used. Its simple structure and the selection of the aforementioned monoalcohols make possible the definition of model systems that give useful information about the kinetics and mechanism of the investigated reactions.…”

Section: Introductionmentioning

confidence: 91%

“…Hydroxy‐terminated fluoropolyethers (FPEs) react with aromatic and cycloaliphatic diisocyanates in polar ethyl acetate (EA), methyl isobutyl ketone (MIBK), and nonpolar hexafluoroxylene (HFX) solvents at NCO:OH = 2 in the presence of the catalysts dibutyltin dilaurate (DBTDL) and 1,4‐diazabiciclo[2,2,2]octane to form NCO end‐capped FPE oligourethanes 1, 2. Catalyzed reactions are sometimes well described by a second‐order rate equation up to high degrees of conversion (90–100% by OH), but often positive deviations from linearity for the second‐order plots {−(2/ a ) × ln[2 − ( a / c )]} versus time have been observed around 40–60% conversions.…”

Section: Introductionmentioning

confidence: 99%

“…Catalyzed reactions are sometimes well described by a second‐order rate equation up to high degrees of conversion (90–100% by OH), but often positive deviations from linearity for the second‐order plots {−(2/ a ) × ln[2 − ( a / c )]} versus time have been observed around 40–60% conversions. These deviations are sensitive toward the solvent nature, temperature, catalyst, and reagent concentration 1, 2. Moreover, the dependence of the second‐order rate coefficients ( k eff ) for these urethane reactions on the reactant concentration was described by curves with maxima2 { k eff = 10 −2 k cat /[DBTDL], where k cat is the catalytic rate coefficient and [DBTDL] is the concentration of the catalyst (mol %) based on diisocyanate}.…”

Section: Introductionmentioning

confidence: 99%

See 4 more Smart Citations

Brachytherapy in total coronary occlusions: Quidquid agis, prudenter agas, et respice finem

Hehrlein¹

2003

Cathet Cardio Intervent

View full text Add to dashboard Cite

In the study by Jain et al. presented in this issue, vascular brachytherapy was performed, applying a betaradiation source (BetaCath TM) to reduce restenosis rates after PTCA of chronic total occlusions (CTOs). The outcome of radiotherapy after percutaneous revascularization of 82 CTOs were analyzed from the RENO registry database, which contains 1,098 consecutive patients undergoing brachytherapy. The results were comparable with those known for brachytherapy of nonocclusive in-stent restenosis with respect to prevention of new restenosis. Why is this finding remarkable?It has become general knowledge that treating chronic coronary occlusions by conventional PTCA is a "different animal" compared with PTCA of plain coronary artery stenosis [1]. Many studies have shown that restenosis rates are extremely high in patients with CTO, even when stenting is performed [2]. Some institutions leave treatment of symptomatic CTOs primarily to the cardiac surgeon. Revascularization of CTO is favorable over medical treatment at least when treated surgically [3]. Therefore, it is important to realize from the report by Jain et al. that restenosis rates of PTCA in CTO have been reduced dramatically using vascular brachytherapy. However, there is the problem of thrombotic vessel occlusion increasing MACE rates, which needs to be understood and acted on. Brachytherapy was plagued from the beginning with the occurrence of late and "late late" thrombosis [4]. Yet only half of all patients of the RENO registry were kept on the combined antiplatelet therapy of aspirin and clopidogrel for a period of 6 months. In addition, new stents were implanted, which tended to reocclude the coronary arteries. What are the lessons we learn from this report? In the words of Gesta Romanorum: "Quidquid agis, prudenter agas, et respice finem." Whatever you do, do it thoughtfully, and kept in mind the goal.Brachytherapy of chronic coronary occlusions requires special attention to the increased risk of thrombotic vessel occlusion. Potential means for reducing the risks of MACE are as follows: apply aspirin and clopidogrel for a minimum period of 12 months (perhaps as lifelong addition of clopidogrel to aspirin medication); use a minimum of new stents to reduce foreign-body activation of platelets; study an increased loading and maintenance dose of clopidogrel in a randomized fashion in the setting of CTO; and, most importantly, remember that CTO patents only benefit from revascularization if viable myocardium is present [5].Mixed results were obtained by other investigators in two recent studies applying brachytherapy in CTO. One group reported similar efficacy and complication rates with intracoronary brachytherapy of occluded in-stent restenosis using a gamma-emitter (Ir-192) compared with irradiation for nonocclusive in-stent restenosis [6]. The other group, however, clearly pointed out that radiotherapy of total occlusions from in-stent restenosis causes increased MACE rates compared with brachytherapy of plain in-stent restenosis [7]. In summary, m...

show abstract

Section: Methodsmentioning

confidence: 99%

Section: Methodsmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 91%

Section: Introductionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

See 3 more Smart Citations

Brachytherapy in total coronary occlusions: Quidquid agis, prudenter agas, et respice finem

Hehrlein¹

2003

Cathet Cardio Intervent

View full text Add to dashboard Cite

show abstract

Fluoropolyethers end-capped by polar functional groups. II. Effect of catalyst and reagents concentration, solvent nature, and temperature on reaction kinetics of ?,?-bis(hydroxy)-terminated fluoropolyethers with cycloalyphatic and aromatic diisocyanates

Mashlyakovskiy

Khomko

Zaiviy

et al. 2000

J. Polym. Sci. A Polym. Chem.

Self Cite

View full text Add to dashboard Cite

A comparative kinetic study of the dibutyltin dilaurate (DBTDL) and 1,4‐diazabicyclo[2,2,2]octane (DABCO) catalyzed reactions of α,ω‐bis(hydroxy)‐terminated fluoropolyethers (FPEs)—Z‐DOLs and Z‐DOL TXs—of various molecular weights and purity, with 4,4′‐dicyclohexylmethane diisocyanate (H12MDI), isophorone diisocyanate (IPDI) and 2,4‐toluene diisocyanate (TDI) was carried out in different solvents. An analytical method was used to follow the kinetics of the reactions at four different temperatures. The rate of NCO disappearance measured by two independent methods—IR spectroscopy and chemical titration were found to be very close. Straight proportionality between rate constants kcat and catalyst concentration was found. But in some cases for the DBTDL catalyzed reactions effect of catalyst saturation along with appearance of the limiting DBTDL concentration Clim below which the rate of reaction was close to zero were observed. Reactivity of Z‐DOLs in the tin‐catalyzed urethane reactions was found to decrease with their storage time at RT due to the slow hydrolysis of the end COOR groups impurities, which give the corresponding acids that act as a strong inhibitor of the DBTDL activity. These acid admixtures have no influence on the DABCO catalyzed reactions. For the DBTDL and DABCO catalyzed reactions of Z‐DOLs with IPDI the dependence of effective rate constants keff (where keff = kcat · 0.01/[DBTDL] and catalyst concentration is taken in mol % based on IPDI) on total reagents concentration were found to be described by curves with a maximum. Critical reagents concentration, after which the relationship keff = f (C) changes from proportional to inverse proportional, seems do not substantially depend on the solvent nature. Hydrogenated analog poly(ethylene glycol) MW 400 (PEG‐400) differs greatly from Z‐DOLs: only steady decrease of keff was observed with increase of reagents concentration C from 5 up to 95 wt %. Activation energies for all the studied reactions are within the range of 10.8–16.7 kcal/mol. © 2000 John Wiley & Sons, Inc. J Polym Sci A: Polym Chem 38: 2579–2602, 2000

show abstract

Fluoropolyethers end‐capped by polar functional groups. IV. A novel approach to the evaluation of reactivities of hydroxy‐terminated ethoxylated fluoropolyethers in the tin(IV)‐catalyzed reactions with isophorone diisocyanate

Khomko

Mashlyakovskiy

Tonelli

2004

J. Polym. Sci. A Polym. Chem.

Self Cite

View full text Add to dashboard Cite

The effect of catalyst dibutyltin dilaurate (DBTDL) on the kinetics of urethane formation reactions of ␣,-bis(hydroxy)-terminated fluoropolyethers Fomblin ® Z-DOL TXs (FPEs) of various molecular weights and poly(oxyethylene) glycol PEG-400 with isophorone diisocyanate (IPDI) in hexafluoroxylene (HFX) and tetrahydrofuran (THF) at 40°C and NCO:OH ϭ 2:1 have been studied in a broad range of catalyst (0.10 -9.00) ϫ10 Ϫ4 M and total reagents (10.0 -60.1 wt %) concentrations. The rate of tin-catalyzed second-order reactions (with respect to diol and diisocyanate) was found to be proportional to the square root of catalyst concentration [DBTDL] 0.5 both in low polar (HFX) and polar (THF) solvents. Effect of catalyst saturation was revealed for all the reaction systems at higher DBTDL concentrations as well as the appearance of the limiting catalyst concentrations C lim below which the rates of reaction were close to zero. Based on these findings new effective rate coefficients have been derived kЈ eff ϭ k cat /(C cat 0.5 Ϫ C lim 0.5 ) that are independent of the total reagent concentration in the range of 10.0 -60.1 wt % ([OH] ϭ 0.10 -0.91 equiv/L). This new approach highlights that the rate of the tin-catalyzed urethane formation reactions of ␣,-bis(hydroxy)terminated fluoropolyethers Z-DOL TXs with IPDI in HFX at 40°C and NCO:OH ϭ 2:1 increases significantly with increasing MW of FPE from 776 up to 3405.

show abstract

Fluoropolyethers end‐capped by polar functional groups. I. Kinetic approach to the reaction of hydroxy‐terminated fluoropolyethers with cycloalyphatic and aromatic diisocyanates

Cited by 4 publications

References 0 publications

Brachytherapy in total coronary occlusions: Quidquid agis, prudenter agas, et respice finem

Brachytherapy in total coronary occlusions: Quidquid agis, prudenter agas, et respice finem

Fluoropolyethers end-capped by polar functional groups. II. Effect of catalyst and reagents concentration, solvent nature, and temperature on reaction kinetics of ?,?-bis(hydroxy)-terminated fluoropolyethers with cycloalyphatic and aromatic diisocyanates

Fluoropolyethers end‐capped by polar functional groups. IV. A novel approach to the evaluation of reactivities of hydroxy‐terminated ethoxylated fluoropolyethers in the tin(IV)‐catalyzed reactions with isophorone diisocyanate

Contact Info

Product

Resources

About