Telechelic Oligomers Research Articles

From olefin cyclopropanation to olefin metathesis through catalyst engineering: recent applications of olefin metathesis to fine organic synthesis and to polymer chemistry

An overview of the recent synthetic breakthroughs brought about by the discovery of new, functional group tolerant late transition metal (Rh and Ru)-based catalysts is proposed. Whereas dirhodium(II)-based complexes promote only carbene transfer reactions to olefins (i.e. olefin cyclopropanation), a few ruthenium-based catalysts can be engineered and fine tuned so as to mediate either carbene-transfer reactions or olefin metathesis. The different outcome of the reactions can be rationalized by the capability of the metal center to coordinate or not both the carbene and the olefin. This quite simple-minded approach indicates that several available coordination sites at the metal center favors metathesis reactions to the prejudice of olefin cyclopropanation. Examples of recent applications in ring opening metathesis polymerizations and copolymerizations include the formation of postpolymers of polydienes, of carbohydrate-substituted polymers and of telechelic oligomers. Application of the same ruthenium-based catalysts in ring-closing metathesis is illustrated by the formation of crown ether analogs, of unsaturated peptides and amino acids, of β-lactams, and of different bicyclic systems.

Telechelic oligomers by halogen atom transfer radical addition

Monodispersed telechelic oligomers have been efficiently prepared by Fe 0−FeCl 3 promoted halogen atom transfer radical of functional telogens and taxogens.

Synthesis of phenetidine-based telechelics and subsequent reactions with water-based curing reagents

The development of soluble telechelics based on aniline are highly desirable due to numerous applications that are possible, especially in the coatings and adhesive industry. Control of molecular length and ease of synthesis lends o-ethoxyaniline to be an ideal candidate for the synthesis of amino-terminated telechelic oligomers. Combined with the higher solubility and reactivity, curing of these functionally reactive oligomers has been accomplished using aqueous formaldehyde, as well as water-dispersed epoxy resins. Spectroscopic studies have been done to characterize the prepolymers, as well as the cured materials. © 1998 John Wiley & Sons, Inc. J Appl Polym Sci 67:1811–1817, 1998

Functionalized polymeric and oligomeric colloids

This paper reviews the author's work to date on functional colloids. Colloids with surface grafts of poly(N-isopropylacrylamide) have been prepared by a macromonomer technique. After removal of the anionic surfactant, the colloids displayed temperature-dependent stability. The preparation of functional colloids that are composed of dispersions of telechelic oligomers has been achieved by ozonizing latices of unsaturated polymers in which the particles were pre-swollen by a hydrophobic solvent. Enzyme immobilization has been carried out by reaction of aldehyde functional colloids with porcine pancreatic lipase. Functional colloids of carboxylic acid-ended oligomer have been further modified with furfuryl amine. The method has been found to be a useful clean technique for the preparation of telechelic oligomers with diene end-groups that can be reacted with dienophile-functionalized polymers. This Diels-Alder reaction yielded amphiphilic networks which may find uses as novel biomaterials. The paper also covers two alternative methods of preparing furan functional colloids of telechelic oligomers: that is, the use of difuran disulphide as a chain transfer agent in emulsion polymerization and the reaction of functional colloids composed of aldehyde functional telechelic oligomers with furfuryl amine. Finally, some preliminary results on the surface functionalization of polymer colloids via water-tolerant Lewis acids are presented.

A one-pot method for the preparation of latices of telechelic oligomers, by ozonolysis of latices of polymers containing main-chain unsaturation

Poly(methyl methacrylate-co-butadiene), Poly(butyl methacrylate-co-butadiene) and Poly(methyl methacrylate-co-2,3-dimethyl butadiene) latices (a.k.a. latexes) were prepared by monomer-starved emulsion polymerization. The polymerizations were followed by GPC. It was found that the molecular-weight distribution did not alter significantly with conversion if the polymerizations were carried out at a feed rate of 0.03 cm3 s−1 per 1000 cm3 of reaction medium and a temperature of 70°C. Slower rates of monomer addition led to broadening of the molecular-weight distribution. The resultant latices were swollen with varying amounts of toluene. Ozonolysis of the swollen and nonswollen latices yielded latices of polymer ozonides. Oxidation, with selenium oxide/hydrogen peroxide reagent, converted the ozonides to latices of carboxylic acid or methyl ketone ended telechelic oligomers. It was found that the molecular weights of the oligomers were a function of toluene concentration. Colloidal stability was found to be a function of end-group structure. Thus, carboxylic acid end groups impart extra stability to the colloid while methyl ketone end groups do not. © 1997 John Wiley & Sons, Inc. J Polym Sci A: Polym Chem 35: 3255–3262, 1997

A one‐pot method for the preparation of latices of telechelic oligomers, by ozonolysis of latices of polymers containing main‐chain unsaturation

A one‐pot method for the preparation of latices of telechelic oligomers, by ozonolysis of latices of polymers containing main‐chain unsaturation

Copolymers of 7-oxabicyclo[2.2.1] heptane with 1,3-dioxane and promesogenic telechelic oligomers thereof

Copolymers of 7-oxabicyclo[2.2.1] heptane (B) (and of its 2-methyl derivatives) with 1,3-dioxane (D) were obtained by cationic copolymerization initiated with benzoylium hexafluoroantimonate. Structure of copolymers was determined by 1H- and 13C-NMR. The proportion of the acetal bonds in copolymers was additionally confirmed in studies of the products of hydrolysis (only the acetal bonds hydrolyze). D is unable to homopolymerize for the thermodynamic reasons and therefore mostly pseudoperiodic copolymers (-DBx-)y are formed. Nevertheless, the reshuffling reactions are responsible for the appearance of “wrong” units. These are: the separate oxymethylene and oxy-1,3-propylene units (P, subunits of D) located between two B units. Only the acetal bonds are cleaved in the acidic hydrolysis with dilute HCl. This gives the promesogenic telechelic oligomers of mostly HO-P-Bx-OH structure. This article is the first to describe successful cationic copolymerization of a cyclic acetal with a cyclic ether. Moreover, the inability of D to homopolymerize gives the thermodynamic basis of the pseudoperiodic copolymer formation. © 1997 John Wiley & Sons, Inc. J Polym Sci A: Polym Chem 35: 1733–1742, 1997

Copolymers of 7‐oxabicyclo[2.2.1] heptane with 1,3‐dioxane and promesogenic telechelic oligomers thereof

Copolymers of 7-oxabicyclo[2.2.1] heptane (B) (and of its 2-methyl derivatives) with 1,3-dioxane (D) were obtained by cationic copolymerization initiated with benzoylium hexafluoroantimonate. Structure of copolymers was determined by 1H- and 13C-NMR. The proportion of the acetal bonds in copolymers was additionally confirmed in studies of the products of hydrolysis (only the acetal bonds hydrolyze). D is unable to homopolymerize for the thermodynamic reasons and therefore mostly pseudoperiodic copolymers (-DBx-)y are formed. Nevertheless, the reshuffling reactions are responsible for the appearance of “wrong” units. These are: the separate oxymethylene and oxy-1,3-propylene units (P, subunits of D) located between two B units. Only the acetal bonds are cleaved in the acidic hydrolysis with dilute HCl. This gives the promesogenic telechelic oligomers of mostly HO-P-Bx-OH structure. This article is the first to describe successful cationic copolymerization of a cyclic acetal with a cyclic ether. Moreover, the inability of D to homopolymerize gives the thermodynamic basis of the pseudoperiodic copolymer formation. © 1997 John Wiley & Sons, Inc. J Polym Sci A: Polym Chem 35: 1733–1742, 1997

On the stereoisomerization in thermal degradation of isotactic poly(propylene)

AbstractThe terminal microstructure of the hydrogenated α,ω‐diisopropenyloligo(propylene) prepared by thermal degradation of isotactic poly(propylene) at 370°C was determined by means of 13C NMR spectroscopy, and therefrom the stereoisomerization reaction of the reacting polymer segment is discussed in relation to polymer dynamics. With respect to the asterisked carbons of the propyl end group CH3CH2*CH2(n‐Pr) and of the isopropyl end group (*CH3)2CH (i‐Pr) formed by hydrogenation, the mole fractions of triads (m meso, r racemo) Fmm = 0.64, Fmr = 0.09, Frr = 0.12 of n‐Pr‐*CH2 differ from the microtacticity of the main chain of telechelic oligomers, and the mole fraction of i‐Pr‐*CH3 is as follows: F(δtζt) + F(δeζe) = 0.74 (m); F(δtζe) + F(δeζt) = 0.26 (r). These results clearly show that the stereoisomerization occurs only at the asymmetric carbon near the end group of the telechelic oligomer. The value of the mole fraction of i‐Pr‐*CH3 is consistent with Fm = 0.73 (Fmm + Fmr) and Fr = 0.27 (Frr + Frm) of n‐Pr‐*CH2 at the outer position of the main chain rather than with Fm = 0.79 (Fmm + Frm) and Fr = 0.21 (Frr + Fmr) at the inner position. These results could be consistently traced by a simulation based on a reaction model including stepwise intramolecular hydrogen abstraction of the tertiary on‐chain macroradical near the center of the main chain before the successive β‐scission. This stepwise back‐biting is estimated to occur once (20%) and twice (80%) via a quasi six‐membered cyclic structure in a transition state, and occurs in a very limited part of the molecular chain.

Synthesis of thiol‐ and carboxyl‐terminated poly(p‐phenylene sulfide) oligomers

AbstractPoly(p‐phenylene sulfide) (PPS) oligomers were synthesized from sodium sulfide (SS) and p‐dichlorobenzene (p‐DCB) in hexamethylphosphoramide (HMPA) under atmospheric pressure. The effects of reaction time, temperature, and monomer ratio on end groups and molecular weight of PPS oligomers were investigated. The results show that the molecular weight is controlled by the above parameters. Thiol‐terminated PPS oligomers were prepared by two routes. One was the polycondensation of p‐DCB with equimolar SS followed by the reaction with an extra amount of SS. The other was the depolymerization of high molecular weight PPS with SS in HMPA. The results show that the second route is the best one for preparation of thiol‐terminated PPS oligomers. Carboxylterminated PPS telechelic oligomers were produced through the reaction of thiol‐terminated PPS oligomers with p‐chlorobenzoic acid.

Preparation of Telechelic Oligomers by the Thermal Degradation of Syndiotactic Polypropylene

Preparation of Telechelic Oligomers by the Thermal Degradation of Syndiotactic Polypropylene

Preparation and characterization of end-reactive oligomers by thermal degradation of polyisobutylene

The chemical structure of the non-volatile oligomers ( M n = 2600–9000) isolated from the polymer residues obtained by the thermal degradation of polyisobutylene at 300 and 320°C was determined by 400 MHz 1H n.m.r. spectroscopy with regard to the reactive end groups. The functional groups formed in the degradation process are as follows: tert-butyl end group (t-Bu), isopropyl end group (i-Pr), terminal trisubstituted double bond (TTD), terminal vinylidene double bond (TVD), and non-terminal trisubstituted double bond (NTTD). The average number of TTD and TVD per molecule ( f t) is in a range from 1.46 to 1.64. This value suggests that 53–67 mol% of the non-volatile oligomers are telechelic oligomers having both TTD and/or TVD, and 39-29 mol% of the oligomers are macromonomer-like oligomers having a double bond at one chain end. Both t-Bu and i-Pr are produced by the intermolecular hydrogen abstraction of primary and tertiary terminal macroradicals, and the subsequent β scission of the resulting on-chain macroradicals at the skeletal CC bond of the main chain yields TTD and TVD. The formation of telechelic oligomer is interpreted by a major contribution of the hydrogen abstraction of volatile radicals, in addition to a minor contribution of the hydrogen abstraction of terminal macroradicals.

Synthesis and characterization of α,ω-hydroxy and nitrato telechelic oligomers of 3,3-(nitratomethyl) methyl oxetane (NIMMO) and glycidyl nitrate (GLYN)

Abstract The synthesis of α,ω-hydroxy telechelic, low-molecular-weight oligomers (degree of polymerization of less than 10) of glycidyl nitrate (GLYN) and 3,3-(nitratomethyl) methyl oxetane (NIMMO) by the activated monomer mechanism is described. Difunctional and/or trifunctional compounds may be prepared. The end-nitration of these compounds has been investigated using dinitrogen pentoxide in dichloromethane to form α,ω-nitrato telechelic oligomers. The materials were characterized by size exclusion chromatography, infrared and nuclear magnetic resonance spectroscopies. Differential scanning calorimetry was used to study the thermal properties of the compounds as they are envisaged to be energetic and fully compatible (miscible) plasticizers for the new generation of energetic binders such as polyNIMMO or polyGLYN, in propellant and explosive applications.

A hydrogel with rubber elasticity transition

AbstractReaction between dimethyldivinylsilane and 3,6‐diazaoctane in the presence of 3‐lithio‐3,6‐diazaoctane yields a new telechelic oligomer, poly(silamine), which consists of alternating 3,3‐dimethyl‐3‐silapentane and N,N′‐diethylethylenediamine units in the main chain. Poly(silamine) shows unique phase transition properties in response to the degree of protonation of amino groups in the polymer. Poly(silamine) also shows a strong interaction with several anions. Due to the interaction between poly(silamine) and anions along with the protonation of amino groups in the poly(silamine), the rubber elasticity of poly(silamine) is drastically changed. A discrete volume change can be observed when the environmental pH of the poly(silamine) gels is varied. This can be explained not only by a change in ionic osmotic pressure but also by a change in the rubber elasticity of the networks in the gel.

Investigations in the competition of the cleavage of the CCl bond of a telogen that exhibits both trichloromethyl and dichloromethylene groups for the redox telomerization of methylmethacrylate and ethylacrylate

The redox telomerizations of ethylacrylate and methylmethacrylate with the 2,2,4,4,4-pentachloromethylbutyrate catalyzed by copper salts or by RuCl 2(PPh 3) 3 were investigated to obtain monodispersed telechelic oligomers. For both monomers, the expected linear products were produced in low yields mainly in the presence of the ruthenium complex. The difunctional telomers Cl 3CCH 2CCl(CO 2CH 3)CH 2CXYCl where X = CH 3 (or X = H) and Y = CO 2CH 3 or CO 2C 2H 5 were obtained as the major products. This was explained by the cleavage of the CCl bond of the dichloromethylene group, more activated by the ester group than the trichloromethyl one. The copper salts led to better yields than the ruthenium complex. The evidence of the formation of such products was given by 1H and 13C NMR spectroscopy.

Block copolymers and telechelic oligomers by end group reaction of polymethacrylates

AbstractBlock copolymers and telechelic oligomers bearing methacrylate moities were obtained by means of a new highly selective end group reaction. Starting from polymethacrylates that were prepared by radical polymerization in the presence of mercaptanes as chain transfer agents, the resulting ester end group linked to the terminal tertiary carbon atom of the polymer backbone can be either transesterified or saponified selectively. The selectivity of the end group reactions was determined by MALDI‐TOF‐mass spectrometry. Polymethacrylate‐b‐poly(ethylene oxide)‐, polymethacrylate‐b‐poly(methacrylic acid)‐ and polymethacrylate‐b‐polysiloxane‐b‐polymethacrylate‐copolymers as well as α,ω‐dihydroxy‐ and α,ω‐dicarboxy‐telechelic polymethacrylates were prepared by applying end group transesterification or end group saponification.

Preparation of .alpha.,.omega.-Diisopropenyloligopropylene by Thermal Degradation of Isotactic Polypropylene

It was found that α,ω-diisopropenyloligoprcpylene (M n = 3300-4800) is prepared as the nonvolatile oligomers isolated from the polymer residues resulting from the thermal degradation of isotactic polypropylene at 370 °C. Their structures were determined by 1 H and 13 C NMR spectroscopies in regard to the reactive end groups. Both the terminal vinylidene double bonds composed of an isopropenyl end group [CH 2 -C(CH 3 )-] and the saturated end group [CH 3 CH 2 CH 2 CH(CH 3 )-] were mainly detected with a molar ratio of about 9 :1. The average number of isopropenyl end groups per molecule f t ) is about 1.8, and therefrom it is indicated that about 80 mol % of the oligomer molecules is symmetric α,ω-diene-oligomer having two terminal isopropenyl groups. This oligopropylene retains highly the stereoregularity (microtacticity) of the original polymer and has a sharper dispersity of molecular weight (M w /M n : ca. 1.5) than the original polymer, in spite of lower molecular weights and T m (ca. 150 °C). This compound is useful as a new telechelic oligomer. These oligomers are considered to be formed by the intramolecular hydrogen abstraction (back-biting) of secondary terminal macroradicals followed by β scission at the end of the main chain (eq 3) and the intermolecular hydrogen abstraction of secondary terminal volatile radicals (eq 4), which are formed by the back-biting and other elementary reactions, followed by β scission.

Polymer-supported reagents as aids in controlled degradation of polymers containing ozonides in the main chain to give telechelic oligomers

The work-up of ozonides derived from the ozonolysis of methacrylate copolymers containing main chain unsaturation has been studied. We have used: periodate supported on Amberlyst A26 (SPIR) (a supported oxidizing agent); polystyrene-supported diphenyl phosphine (SPR) (a mild supported reducing agent) and borohydride supported on Amberlyst A26 (BER) (a more powerful supported reducing agent). Poly(butyl methacrylate-cobutadiene)s were synthesized by starve fed emulsion polymerization. These materials, and the homopolymer, poly(butyl methacrylate), were then ozonized at different temperatures and worked up with each of the reagents listed above. The differing work-ups generated telechelic oligomers in good yield (99%+). Changes in molecular weight with ozonization temperature were observed. Aldehyde end-groups were detected by 1H- and 13C-NMR. Hydroxyl end-groups were observed by FTIR and 13C-NMR spectroscopy. The presence of hydroxyl groups was also further confirmed by forming the tosylate. Carboxyl groups were observed by FTIR and 13C-NMR and quantified by titration. SPR-generated oligomers had approximately 80% of the chain-ends Adehyde functional, BER and SPIR gave oligomers with 99+% hydroxyl and carboxyl functionality, respectively.

Degradative Routes to Telechelic Oligomers and Macromonomers

A variety of telechelic oligomers with terminal aldehyde, hydroxyl, ketone or carboxylic acid end groups can be synthesized by ozonolyses of suitable free radical copolymers containing small amounts of randomly distributed C=C bonds. These bonds can be introduced using either a diene or an acetylene as comonomer. The average molecular weights of the oligomers are controlled by the C=C content, and the nature of the end groups by the choice of diene or acetylene and by the procedures used to work up the ozonides. Potentially macromonomeric oligomers can be synthesized by the photolysis of copolymers containing small amounts of alkyl vinyl or aryl vinyl ketone units. Telechelic oligomers can be chain-extended by a variety of means, including by Michael additions, depending on the nature of the end groups.

Chain extension and crosslinking of telechelic oligomers—I. Michael additions of bisamines to bismaleimides and bis(acetylene ketone)s

Some commercial amine-ended oligo(oxypropylene)s and oligo(oxyethylene- b-oxypropylene)s, and an amine-ended oligo(dimethylsiloxane), have been chain extended via Michael additions with some simple bismaleimides and bis(acetylene ketone)s. The polymers so-formed have molar masses of up to ca 20,000, corresponding to degrees of polymerization of the starting oligomers of up to ca 15. The polymers are either linear (and therefore soluble) or crosslinked, depending upon the starting materials and the precise conditions of preparation. Also, block copolymers can be prepared by chain extending mixtures of bisamine-ended oligomers, or by reacting an amine-ended oligomer with one having terminal maleimide groups.