Acyclic diene metathesis polymerization

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The acyclic diene metathesis ( english a cyclic d iene met Athesis ), also ADMET polymerization called, is a variant of the alkene metathesis , wherein Di olefins having terminal double bonds (α, ω-dienes) in a step-growth reaction running equilibrium reaction in the presence of transition metal - carbene complexes as catalysts to give linear polymers having olefinic double bonds in the polymer backbone, with elimination ofEthene react.

Metathesis reaction of α, ω-diolefins

history

Acyclic diene metathesis polymerization was first developed in 1991 by Kenneth B. Wagener using higher molecular weight polymers using the example of the polymerization of 1,9-decadiene to polyoctenamer (here called polyoctenylenes) and 1,5-hexadiene to 1,4-polybutadiene with the catalyst tungsten ( VI) chloride WCl 6 and the cocatalyst ethylaluminum dichloride EtAlCl 2 described.

ADMET polymerization of 1,9-decadiene to polyoctenamer

The quantitative hydrogenation of the olefinic double bonds in the polymer backbone yields a saturated polymer chain that is similar to that of a completely linear polyethylene . The polymer referred to by KB Wagener as polyoctenylene is similar to the polyoctenamer obtainable from cyclooctene by ring opening metathesis polymerization ( ROMP ),

ROMP from Cyclooctene to Polyoctenamer

a as a trans-polyoctenamer rubber (engl. t rans-poly o ctylene r ubber known, TOR) rubber additive (Vestenamer 8012 ® of the company. Evonik), which, however, up to 25 wt .-% of macrocycles with molar masses up to 100.000 g · Mol −1 .

Previous observations that the WCl 6 / EtAlCl 2 / EtOH catalyst system can promote both ROMP and olefin disproportionation suggested that both chemical conversions should be based on the same reaction.

The reaction mechanism proposed by Yves Chauvin in 1971 for olefin metathesis via metallacyclobutane turned out to be groundbreaking for the understanding of the metathesis reactions of the ROMP and ADMET types. The work that began in the late 1980s in KB Wagener's group did not yet provide any useful polymers in the acyclic diene metathesis polymerization with WCl 6 / EtAlCl 2 catalysts, which was initially called "α, ω-diene polycondensation" .

It was only with the neutral and Lewis acid-free tungsten and molybdenum complexes found by Richard R. Schrock at the same time that the reliable suppression of vinyl polymerization in favor of olefin metathesis and thus the production of higher molecular weight polymers succeeded.

Typical W- and Mo-based Schrock catalysts

Tungsten carbene complexes catalyze the olefin metathesis significantly faster and the tungsten cyclobutanes formed are more stable than the corresponding molybdenum compounds, but less tolerant of functional groups in the α, ω-diene. The molybdenum catalysts in turn are easier to handle and allow the acyclic diene metathesis polymerization of u. a. Esters, carbonates, ethers, aromatic amines and siloxanes.

In 1992 the working group of RH Grubbs described the first olefin metathesis catalysts based on ruthenium compounds ( Grubbs catalysts ), which were much more stable in air and less sensitive to functional groups in the dienes and solvents. The tricyclohexylphosphine complexes are significantly more stable than the triphenylphosphine analogues. The most prominent representative of the so-called 1st generation of Grubbs catalysts for acyclic diene metathesis polymerization is benzylidenebis (tricyclohexylphosphine) dichlororuthenium

Typical Grubbs I catalyst

1st generation Grubbs catalysts are characterized by a very low (<5%) isomerization rate in acyclic diene metathesis polymerization.

A further development with greater stability towards oxygen and water - and thus also easier handling - are the so-called 2nd generation Grubbs catalysts with an imidazole-based ligand, which also have higher activity in olefin metathesis than that of Schrock's molybdenum complexes comes close. 2nd generation Grubbs catalysts have a much stronger tendency to isomerization (up to 90%), but this can be suppressed to less than 10% by adding [1,4-benzoquinone].

By replacing the unsubstituted benzylidene ligand with a benzylidene ligand with a chelating ortho-isopropyloxy group, the so-called Hoveyda-Grubbs catalysts are obtained , in which one (1st generation) or both (2nd generation) of tricyclohexylphosphine is obtained -Ligands can be replaced, so that phosphine-free complexes are also accessible. The chiral ruthenium complexes obtained are characterized by stability in air and high activity for stereoselective conversions (up to> 98%), even in reactions in air, with unpurified solvents and with starting compounds that otherwise only polymerize with molybdenum-based catalysts.

The Hoveyda-Grubbs catalysts are easily accessible from the corresponding Grubbs catalysts in a single-stage reaction and are more robust than these. Due to their high stability, the catalysts can be chromatographed and recovered, but they are also more expensive and, with an often longer induction phase, somewhat more complicated to handle. Further modifications are also suitable for acyclic diene metathesis polymerization, where bulky and electron-rich ligands cause a higher degree of polymerization and very short initial phases.

As 3rd generation Grubbs catalytic converters, newer variants are designated with z. B. 3-bromopyridine ligands with drastically shortened induction phases or with less bulky ligands (e.g. tolyl instead of mesityl units), which link allylic olefins more efficiently.

With the modern transition metal catalysts many functional α, ω-dienes, z. B. also from renewable raw materials, such. B. 10-undecen-1-ol , can be converted to useful polymers under mild conditions by means of acyclic diene metathesis polymerization.

Yves Chauvin, Robert H. Grubbs and Richard R. Schrock received the Nobel Prize in Chemistry in 2005 for the “Development of Metathesis Reactions in Organic Synthesis”.

Characteristics of acyclic diene metathesis polymerization

In olefin metathesis there is a statistical redistribution of functional groups through the exchange of alkylidene groups between two different olefin molecules.

metathesis

Because of their lower steric hindrance, monosubstituted terminal double bonds react much more easily than multiply substituted ones.

Schrock catalysts can also polymerize more sterically demanding dienes and are generally more active than Grubbs catalysts, which in turn tolerate many different functional groups. Both types of catalyst can, depending on the chemical nature of the ligands and with different activity, favor both ROMP and ADMET equilibrium polymerizations of olefins by metathesis.

Hérrison and Chauvin elucidated the reaction mechanism of alkene metathesis , according to which a metallacyclobutane is formed in a reversible [2 + 2] cycloaddition of a metal carbene complex with an olefin, from which a new metal carbene complex and a new olefin are formed in a [2 + 2] retrocycloaddition. While in the acyclic diene metathesis polymerization the equilibrium is shifted (entropically) in the direction of the polymer by the removal of a small molecule (ethene) and the reverse reaction is suppressed, the driving force in the ROMP reaction is the change in enthalpy due to the removal of the ring strain of the cycloalkenes .

In contrast to ROMP, ADMET polymerizations are carried out in bulk in order to avoid competing equilibrium reactions and to facilitate the release of ethene. In contrast to the other known metathesis reactions, acyclic diene metathesis is not a chain growth reaction with addition of monomers to the active chain end of a macromolecule, but a polycondensation reaction (with metal complex catalysis), in which monomers react gradually to form dimers, which in turn condense to tetramers, etc. Like all step growth reactions, the ADMET reaction also requires very high conversions (> 99% of the reactive groups) in order to obtain polymers with high molar masses. This kinetic behavior clearly contrasts with a chain growth reaction, such as e.g. B. the polymerization of standard olefins, in which conversion rates of 90% are already excellent.

The Carothers equation applicable to linear step growth reactions :

X̅ n = 1/1-p

links the degree of polymerization X̅ n (more precisely: the number average of the degree of polymerization , DP ) with the degree of conversion p of a polycondensation reaction. At a conversion of 99%, an average degree of polymerization of 100 is achieved. Two high molecular weight polymer chains are only linked when the conversion is high, which considerably reduces the number of polymer molecules in the reaction space. It also follows from this that the catalyst activity must be high over the entire polymerization cycle.

The presence of even small amounts of impurities in the α, ω-diene monomers - in particular monoolefins which lead to end-capping - likewise reduces the degree of polymerization dramatically.

The modified Carothers equation with f imp as the proportion of impurities in the amount of monomer:

X̅ n = 2 + f imp / 2 + f imp -2p

results in a degree of polymerization reduced from 100 to 67 for a degree of polymerization of 0.99 and an f imp of 1%.

It follows from this that high molecular weight polymers can only be produced by ADMET polycondensation with highly pure diene monomers and with complete removal of the ethene formed (carrying out the reaction in a vacuum or degassing in an inert gas stream). The polymers produced in the ADMET polyreaction under equilibrium conditions have the most probable molecular weight distribution of polycondensations, i.e. a polydispersity ( polydispersity index PDI ) M w / M n of 2, which corresponds to an ideal Schulz-Flory distribution .

The olefinic polymers formed by the ADMET reaction are predominantly (75-95%, typically> 90%) in the trans configuration.

Since no chain transfer occurs in ADMET reactions as in free radical polymerizations, no branched polymers are formed either. The mild reaction conditions and the absence of side reactions enable the synthesis of defect-free polymers with easily controllable molecular weights and polydispersities and thus also microstructures.

Applications

ADMET polymerization enables the controlled construction of linear polymers with functions or structures that are separated by a certain number of methylene groups and a C = C double bond. So z. B. from undecenylundecenoate by ADMET polymerization an unsaturated polyester in which every 20 carbon atoms is an ester function and a double bond.

ADMET polymerisation of dienes from renewable raw materials

Similarly, the sulfonate ester undecenyl undecene sulfonate yields unsaturated aliphatic polysulfonates with average molar masses M n up to 37,000 g mol −1 in ADMET polymerization , which are hydrogenated smoothly on a Pd / C catalyst to give the corresponding saturated polysulfonates.

Also polyurethanes are in the same manner starting from the bio-based feedstock 10-undecenoic acid or its azide and 10-undecene-1-ol represented by ADMET polymerization.

The molar masses that can be achieved through ADMET polymerization of α, ω-dienes with polar functional groups are generally lower than through radical polymerization, but this enables their thermoplastic processing, which is the case with polar polycondensates with M n > approx. 30,000 g · mol −1 becomes problematic.

In addition, polymers with defined molar masses, such as. B. closely distributed and unbranched polyethylenes, copolymers, z. B. ethylene vinyl acetate EVA and with unusual primary structures (polymer architectures), such as. B. (highly branched hyperbranched ) polymers or poly rotaxanes accessible.

Monomers with acidic hydrogen atoms, e.g. B. 4-vinylbenzylphosphonic acid, poison ADMET polymerization catalysts, but can also be used in ADMET copolymers after reaction with protective groups, which are being discussed for future use as proton-conducting membranes for fuel cells .

ADMET polymerisation is often used for monomers made from renewable raw materials, e.g. B. reaction products of 10-undecenoic acid , with diene character. and also enables the production of block copolymers with thermoplastic properties.

With the unsaturated dicarboxylic acid itaconic acid ( accessible from molasses by fermentation ), after reaction with 10-undecen-1-ol and subsequent ADMET polymerization, an unsaturated polyester with a free vinyl group of itaconic acid, to which thiols and amines can be added in a Michael addition .

Functionalized α, ω-dienes, e.g. B. 2- (Undec-10-en-1-yl) tridec-12-en-1-yl-acrylate

Functionalization of ADMET polymers by subsequent thiol-ene click reaction

can also be converted into a number of symmetrical and functional monomers after thiol-Michael addition and oxidation of the thioether formed to the sulfone . The high molecular weight ADMET polymerization products can be further functionalized by a thiol click reaction on the double bonds in the polymer backbone.

ADMET polymerization of α, ω-dienes in the presence of functional α-monoolefins produces telechelic , i.e. H. Oligomers with reactive end groups that are suitable for the production of block copolymers.

literature

Review article

  • NF Sauty, LC da Silva, MD Schulz, CS Few, KB Wagener: Review Article: Acyclic diene metathesis polymerization and precision polymers . In: Appl. Petrochemical. Res. Band 4 , 2014, p. 225-233 , doi : 10.1007 / s13203-014-0045-2 .
  • P. Atallah, KB Wagener, MD Schulz: ADMET: The future revealed . In: Macromolecules . tape 46 , no. 12 , 2013, p. 4735-4741 , doi : 10.1021 / ma400067b .
  • C. Simocko, P. Atallah, KB Wagener: A brief examination of the latest ADMET chemistry . In: Current Organic Chemistry . tape 17 , no. 22 , 2013, p. 2749-2763 (15) .
  • H. Mutlu, L. Montero de Espinosa, MAR Meier: Critical Review: Acyclic diene metathesis: a versatile tool for the construction of defined polymer architectures . In: Chem. Soc. Rev. Band 40 , 2011, p. 1404-1445 , doi : 10.1039 / B924852H .
  • KL Opper, KB Wagener: ADMET: Metathesis polycondensation . In: J. Polym. Sci. Part A: Polym. Chem. Band 49 , no. 4 , 2011, p. 821-831 , doi : 10.1002 / pola.24491 .
  • RR Schrock: Recent advances in high oxidation state Mo and W imido alkylidene chemistry . In: Chem. Rev. Band 109 , no. 8 , 2009, p. 3211-3226 , doi : 10.1021 / cr800502p .
  • TW Baughman, KB Wagener: Recent advances in ADMET polymerization . In: Adv. Polym. Sci .: Metathesis Polymerization . tape 176 . Springer, 2005, ISBN 3-540-23358-X , pp. 1-42 , doi : 10.1007 / b101315 .
  • SE Lehman Jr, KB Wagener: Catalysis in acyclic diene metathesis diene (ADMET) polymerization . In: B. Rieger, LS Baugh, S. Kacker, S. Stiegler (eds.): Late transition metal polymerization catalysis . Wiley-VCH, 2003, ISBN 3-527-30435-5 , pp. 193-230 .

Individual evidence

  1. ^ A b K. B. Wagener, JM Boncella, JG Nel: Acyclic diene metathesis (ADMET) polymerization . In: Macromolecules . tape 24 , no. 10 , 1991, pp. 2649-2657 , doi : 10.1021 / ma00010a001 .
  2. ^ JE O'Gara, KB Wagener, SF Hahn: Acyclic diene metathesis (ADMET) polymerization. Synthesis of perfectly linear polyethylene . In: Makromol. Chem., Rapid Commun. tape 14 , no. 10 , 1993, p. 657-662 , doi : 10.1002 / marc.1993.030141006 .
  3. ↑ Evonik Industries, Vestenamer 8012: The rubber additive with unique properties, PDF ( Memento from February 27, 2015 in the Internet Archive )
  4. ↑ N. Calderon, HY Chen, KW Scott: Olefin metathesis - A novel reaction for skeletal transformations of unsaturated hydrocarbons . In: Tetrahedron Lett. tape 34 , 1967, p. 3327-3329 , doi : 10.1016 / S0040-4039 (01) 89881-6 .
  5. ↑ a b J.-L. Hérrison, Y. Chauvin: Catalysis of olefin transformations by tungsten complexes. II. Telomerization of cyclic olefins in the presence of acyclic olefins . In: Makromol. Chem. Band 141 , 1971, p. 161–176 , doi : 10.1002 / macp.1971.021410112 .
  6. ^ M. Lindmark-Hamberg, KB Wagener: Acyclic metathesis polymerization: the olefin metathesis reaction of 1,5-hexadiene and 1,9-decadiene . In: Macromolecules . tape 20 , no. 11 , 1987, pp. 2949-2951 , doi : 10.1021 / ma00177a053 .
  7. ↑ CJ Schaverien, JC Dewan, RR Schrock: Multiple metal-carbon bonds. 43. Well-characterized, highly active, Lewis acid free olefin metathesis catalysts . In: J. Amer. Chem. Soc. tape 108 , no. 10 , 1986, pp. 2771-2773 , doi : 10.1021 / ja00270a056 .
  8. ↑ JS Murdzek, RR Schrock: Well-characterized olefin metathesis catalysts did contain molybdenum . In: Organometallics . tape 6 , 1987, pp. 1373-1374 , doi : 10.1021 / om00149a048 .
  9. ^ DW Smith, Jr., KB Wagener: Acyclic diene metathesis (ADMET) polymerization. Design and synthesis of unsaturated poly (carbosiloxanes) . In: Macromolecules . tape 26 , no. 7 , 1993, pp. 1633-1642 , doi : 10.1021 / ma00059a022 .
  10. ↑ ST Nguyen, LK Johnson, RH Grubbs, JW Ziller: Ring-opening metathesis polymeriszation (ROMP) of norbornene by a Group VIII carbine complex in protic media . In: J. Am. Chem. Soc. tape 114 , no. 10 , 1992, pp. 3974-3975 , doi : 10.1021 / ja00033a053 .
  11. ^ K. Brzezinska, PS Wolfe, MD Watson, KB Wagener: Acyclic diene metathesis (ADMET) polymerization using a well-defined ruthenium-based metathesis catalyst . In: Macomol. Chem. Phys. tape 197 , no. 6 , 1996, pp. 2065-2074 , doi : 10.1002 / macp.1996.021970622 .
  12. ↑ a b P. A. Foukou, MA R Meier: Use of a renewable and degradable monomer to study the temperature-dependent olefin isomerization during ADMET polymerizations . In: J. Amer. Chem. Soc. tape 131 , no. 5 , 2009, p. 1664–1665 , doi : 10.1021 / ja808679w .
  13. ↑ M. Scholl, S. Ding, CW Lee, RH Grubbs: Synthesis and activity of a new generation of ruthenium-based olefin metathesis catalysts coordinated with 1,3-dimesityl-4,5-dihydroimidazol-2-ylidene ligands . In: Org. Lett. tape 1 , no. 6 , 1999, p. 953-956 , doi : 10.1021 / ol990909q .
  14. ↑ PA Foukou, MA R Meier: Studying and suppressing olefin isomerization side reactions during ADMET polymerizations . In: Macromol. Rapid Commun. tape 31 , no. 4 , 2010, p. 368-373 , doi : 10.1002 / marc.200900678 .
  15. ^ JJ Van Veldhuizen, SB Garber, JS Kingsbury, AH Hoveyda: A recyclable chiral Ru catalyst for enantioselective olefin metathesis. Efficient catalytic asymmetric ring-opening / cross metathesis in air . In: J. Am. Chem. Soc. tape 124 , no. 18 , 2002, p. 4954-4955 , doi : 10.1021 / ja020259c .
  16. ^ GC Vougioukalakis, RH Grubbs: Ruthenium-based heterocyclic carbene-coordinated olefin metathesis catalysts . In: Chem. Rev. Band 110 , no. 3 , 2002, p. 1746-1787 , doi : 10.1021 / cr9002424 .
  17. ↑ FC Courchey, JC Sworen, A. Coronado, RB Wagener: The utility of Hoveyda-type catalysts in ADMET chemistry: Sterics versus electronics . In: J. Mol. Catal. A: Chemical . tape 254 , no. 1–2 , 2006, pp. 111-117 , doi : 10.1016 / j.molcata.2006.02.073 .
  18. ^ JA Love, JP Morgan, TM Trnka, RH Grubbs: A practical and highly active ruthenium-based catalyst that effects the cross metathesis of acrylonitrile . In: Angew. Chem. Int. Ed. tape 41 , no. 21 , 2002, p. 4035-4037 , doi : 10.1002 / 1521-3773 (20021104) 41:21 <4035 :: AID-ANIE4035> 3.0.CO; 2-I .
  19. ^ IC Stewart, CJ Douglas, RH Grubbs: Increased efficiency in cross-metathesis reactions of sterically hindered olefins . In: Org. Lett. tape 10 , no. 3 , 2008, p. 441-444 , doi : 10.1021 / ol702624n .
  20. ^ O. Kreye, T. Tóth, MAR Meier: Poly- α, β- unsaturated aldehydes derived from castor oil via ADMET polymerization . In: Eur. J. Lipid Sci. Technol. tape 113 , no. 1 , 2011, p. 31–38 , doi : 10.1002 / ejlt.201000108 .
  21. ↑ V. Dragutan, I. Dragutan, AT Balaban: 2005 Nobel Prize in Chemistry: AWARDED FOR THE DEVELOPMENT OF THE metathesis REACTION IN ORGANIC SYNTHESIS . In: Platinum Metals Rev. Band 50 , no. 1 , 2006, p. 35-37 , doi : 10.1595 / 147106706x94140 ( 2005 Nobel Prize in Chemistry: AWARDED FOR THE DEVELOPMENT OF THE METATHESIS REACTION IN ORGANIC SYNTHESIS ).
  22. ^ KB Wagener, DW Smith: Acyclic diene metathesis polymerization: synthesis and characterization of unsaturated poly [carbo (dimethyl) silanes] . In: Macromolecules . tape 24 , no. 23 , 1991, pp. 6073-6078 , doi : 10.1021 / ma00023a004 .
  23. ^ A b TW Baughman, KB Wagener: Recent advances in ADMET polymerization . In: Adv. Polym. Sci .: Metathesis Polymerization . tape 176 . Springer, 2005, ISBN 3-540-23358-X , pp. 1-42 , doi : 10.1007 / b101315 .
  24. ^ A b A. Rybak, MAR Meier: Acyclic diene metathesis with a monomer from renewable resources: Control of molecular weight and one-step preparation of block copolymers . In: ChemSusChem . tape 1 , no. 6 , 2008, p. 542-547 , doi : 10.1002 / cssc.200800047 .
  25. ^ RR Parkhurst, S. Balog, C. Weder, YC Simon: Synthesis of poly (sulfonate esters) s by ADMET polymerization . In: RSC Adv. Band 4 , no. 96 , 2014, p. 53967-53974 , doi : 10.1039 / C4RA08788G .
  26. ↑ T. Lebarbé, AS More, PS Sane, E. Grau, C. Alfos, H. Cramail: Bio-based aliphatic polyurethanes through ADMET polymerization in bulk and green solvent . In: Macromol. Rapid Commun. tape 35 , no. 4 , 2014, p. 479-483 , doi : 10.1002 / marc.201300695 .
  27. ^ MD Watson, KB Wagener: Ethylene / vinyl acetate copolymers via acyclic diene metathesis polymerization. Examining the effect of "long" precise ethylene run lengths . In: Macromolecules . tape 33 , no. 15 , 2000, pp. 5411-5417 , doi : 10.1021 / ma9920689 .
  28. ↑ N. Momcilovic, PG Clark, AJ Boydston, RH Grubbs: One-pot synthesis of polyrotaxane via acyclic diene metathesis polymerization of supramolecular monomers . In: J. Am. Chem. Soc. tape 133 , no. 47 , 2011, p. 19087–19089 , doi : 10.1021 / ja208515r .
  29. ^ MD Schulz, KB Wagener: Precision polymers through ADMET polymerizations . In: Macromol. Chem. Phys. tape 215 , no. 20 , 2014, p. 1936–1945 , doi : 10.1002 / macp.201400268 .
  30. ↑ D. Markova, KL Opper, M. Wagner, M. Klapper, KB Wagener, K. Müllen: Synthesis of proton conducting phosphonic acid-functionalized polyolefins by the combination of ATRP and ADMET . In: Polym. Chem. Band 4 , 2013, p. 1351-1363 , doi : 10.1039 / C2PY20886E .
  31. ^ H. Mutlu, L. Montero de Espinosa, MAR Meier: Critical Review: Acyclic diene metathesis: a versatile tool for the construction of defined polymer architectures . In: Chem. Soc. Rev. Band 40 , 2011, p. 1404-1445 , doi : 10.1039 / B924852H .
  32. ↑ a b T. C. Mauldin, EF Spiegel, MR Kessler: Block copolymers derived from the acyclic diene metathesis (ADMET) polymerization of a modified vegetable oil . In: Polymer Preprints . tape 52 , no. 1 , 2011, p. 107-108 ( online ( memento of February 24, 2015 in the Internet Archive ) [PDF; accessed January 27, 2015]). Block copolymers derived from the acyclic diene metathesis (ADMET) polymerization of a modified vegetable oil ( Memento of the original from February 24, 2015 in the Internet Archive ) Info: The archive link was automatically inserted and not yet checked. Please check the original and archive link according to the instructions and then remove this notice.  @1@ 2Template: Webachiv / IABot / library.sut.ac.th
  33. ↑ A. Lv, Z.-L. Li, F.-S. You, Z.-C. Li: Synthesis, functionalization, and controlled degradation of high molecular weight polyester from itaconic acid via ADMET polymerization . In: Macromolecules . tape 47 , no. 22 , 2014, p. 7707-7716 , doi : 10.1021 / ma5020066 .
  34. ↑ JA van Hensbergen, TW Gaines, KB Wagener, RP Burford, AB Lowe: Functional α, ω- dienes via thiol-Michael chemistry: synthesis, oxidative protection, acyclic diene metathesis (ADMET) polymerization and radical thiol-ene modification . In: Polym. Chem. Band 5 , no. 10 , 2014, p. 6225-6235 , doi : 10.1039 / C4PY00783B .
  35. ^ JE Schwendeman, RB Wagener: Synthesis of amorphous hydrophobic telechelic hydrocarbon diols via ADMET polymerization . In: Macromol. Chem. Phys. tape 210 , no. 21 , 2009, p. 1818–1833 , doi : 10.1002 / macp.200900270 .