Mechanism of Olefin Metathesis (exchange double bonds)

Transcription

1 Sythesis of Polymers Prof. Paula ammod Lecture 33: ig-peig Metathesis Polymerizatio, xidative ouplig, Electrochemical Polymerizatio, ase Study: Electro-Active Polymers SFP - Useful for modifyig surfaces - Geeratio of high adhesive surfaces Mechaism of lefi Metathesis (exchage double bods) Trasalkylatio ' ' ' Trasalkylideatio ' ' ' Actual ate ' The double bods exchage yclic Alkee itatio: Professor Paula ammod, Sythesis of Polymers Fall 2006 materials, MIT peourseware ( Massachusetts Istitute of Techology, Date.

2 ig peig Metathesis Polymerizatio (MP) atalytic Process Efficacy of process is depedet o catalyst Polymer is also depedet o moomer structure Potetial moomers 1. = must be i a straied rig system MP (o strai) cyclooctae MP % coversio far from equilibrium cyclobutae MP % coversio cyclopetae (ot as straied) MP [M] eq Moo, Bi ad Tricyclic MP Moomers , Sythesis of Polymers, Fall 2006 Lecture 33 Prof. Paula ammod Page 2 of 10 itatio: Professor Paula ammod, Sythesis of Polymers Fall 2006 materials, MIT peourseware ( Massachusetts Istitute of Techology, Date.

3 tricyclic m eactivity of Bi ad Tricyclic >> Moocyclic 2 Me A B 2 Me Examples of orboradiees 2. For typical moocyclic alkees: Substituets available are limited oxyge at bridge piacle 2,, -, Must use somethig less reactive. 3. a t polymerize cyclic alkee with -substituet directly o = bod. 3 Wo t udergo MP. Whereas 3 will udergo MP. For bicyclics, (ad tricyclics) , Sythesis of Polymers, Fall 2006 Lecture 33 Prof. Paula ammod Page 3 of 10 itatio: Professor Paula ammod, Sythesis of Polymers Fall 2006 materials, MIT peourseware ( Massachusetts Istitute of Techology, Date.

4 much faster rx rates always get % coversio due to high rig strai less proe to secodary rearragemets of backboe (shufflig) side reactios with catalyst are miimized ca itroduce some polar substituets ex Ac 2 Schrock catalysts: W, Mo (MIT) Grubbs catalyst: u (altech) 2 Ac l F orboree will polymerize i its fuctioalized forms fuctioalized polymers Ac 2 Ac 2 Ac 2 2 Ac Ed-appig Livig MP Wittig eactio , Sythesis of Polymers, Fall 2006 Lecture 33 Prof. Paula ammod Page 4 of 10 itatio: Professor Paula ammod, Sythesis of Polymers Fall 2006 materials, MIT peourseware ( Massachusetts Istitute of Techology, Date.

5 Schrock Iitiator Aldehyde [Mo] X [Mo] = Mo(Ar)(-t-Bu) 2 X [Mo]= [Mo] [Mo]= Livig MP i very rapid with specific catalyst tolerat catalysts for fuctioal groups very low PDI perfect polymers almost ature-like X desired ed group oductig Polymers Mo X ojugated polymers that allow e - trasfer alog chai. Polyacetylee X , Sythesis of Polymers, Fall 2006 Lecture 33 Prof. Paula ammod Page 5 of 10 itatio: Professor Paula ammod, Sythesis of Polymers Fall 2006 materials, MIT peourseware ( Massachusetts Istitute of Techology, Date.

6 chais should be orieted macroscopically e- π-orbitals overlappig huge delocalizatio of e - e - ca move back ad forth o polymer chai cojugatio cojugatio polyacetylee from (gas) slightly explosive 1 st record of polyacetylee 2- type polym. (gas bubbled through solvet with solid phase catalyst) powder itractable (T m too high isoluble) James Feast moomer F 3 W/S F 3 W/Al F 3 heat Durham oute Sythesis of Diblocks , Sythesis of Polymers, Fall 2006 Lecture 33 Prof. Paula ammod Page 6 of 10 itatio: Professor Paula ammod, Sythesis of Polymers Fall 2006 materials, MIT peourseware ( Massachusetts Istitute of Techology, Date.

7 L[W] eq. L[W] catalyst orboree L[W] meq. feast moomer L[W] m ' L[W] ' m ' m TriBlock opolymers otaiig Durham Polyacteylee , Sythesis of Polymers, Fall 2006 Lecture 33 Prof. Paula ammod Page 7 of 10 itatio: Professor Paula ammod, Sythesis of Polymers Fall 2006 materials, MIT peourseware ( Massachusetts Istitute of Techology, Date.

8 F 3 F 3 or [Mo] Mo L [Mo] LD F or cojugated aldehyde for Wittig F 3 F 3 o,30mi -200 Shirakawa: coated walls of Schlak tube with catalyst, the admitted acetylee gas form a thi film o glass walls silver, brittle, isoluble, itractable cofirmed e - coductivity 0.1 S/cm 1 S/cm Difficult to isolate acetylee , Sythesis of Polymers, Fall 2006 Lecture 33 Prof. Paula ammod Page 8 of 10 itatio: Professor Paula ammod, Sythesis of Polymers Fall 2006 materials, MIT peourseware ( Massachusetts Istitute of Techology, Date.

9 ojugated Polymers (commo) eeger ad MacDiarmid Pyrrole polypyrole Ailie 2 x y polyailie Thiophee S S polythiophee favorable properties i terms of stability ca be fuctioalized xidatio ad eductio Approaches to Polymerizatio - Electrochemical - hemical (itroductio of a reaget) cathode aode 1. eductio at cathode electrolyte e xidatio at aode radical aio ' -e radical catio Geerate combiatio , Sythesis of Polymers, Fall 2006 Lecture 33 Prof. Paula ammod Page 9 of 10 itatio: Professor Paula ammod, Sythesis of Polymers Fall 2006 materials, MIT peourseware ( Massachusetts Istitute of Techology, Date.

10 fte radicals combie to geerate dioic species. Electropolymerizatio of Pyrrole Iitiatio. e - Propagatio. 2 2 x... x1 2 e - Termiatio. 2 x x , Sythesis of Polymers, Fall 2006 Lecture 33 Prof. Paula ammod Page 10 of 10 itatio: Professor Paula ammod, Sythesis of Polymers Fall 2006 materials, MIT peourseware ( Massachusetts Istitute of Techology, Date.