ROMP synthesis of novel thermo‐, pH‐, and salt‐responsive (co)polymers containing the morpholino functional group

We report the ring‐opening metathesis polymerization (ROMP) synthesis of novel (co)polymers containing the multiresponsive morpholino functional group [(3aR,7aS)?2‐(2‐morpholinoethyl)?3a,4,7,7a‐tetrahydro‐1H?4,7‐epoxyisoindole‐1,3(2H)‐dione ( M1 )]. All (co)polymers were prepared with the Grubbs' first generation initiator, RuCl₂(PCy₃)₂CHPh, in CH₂Cl₂ or CH₂Cl₂/2,2,2‐trifluoroethanol solvent mixtures. M1 homopolymers exhibit a pH dependent aqueous solubility being fully soluble below pH 5.0 and above pH 6.0. At these intermediate values, the polymers exhibit molecular weight (MW) independent inverse temperature dependent solubility with measured cloud points (T_CP) of 86 °C at pH 5.0 and 79 °C at pH 6.0. In the case of the lowest MW homopolymer (absolute MW of 9950 g/mol), there was a clear dependence of the T_CP on the homopolymer solution concentration and varied over the range 78–88 °C. The T_CP could be further tuned via the preparation of novel AB statistical copolymers. Incorporation of a permanently cationic comonomer as a more hydrophilic species resulted in an increase of the T_CP at low incorporations (up to 10 mol %) and the complete disappearance of any temperature dependent solubility at 20 mol %. In a complementary approach, the T_CP could also be lowered by the preparation of statistical copolymers of M1 with a more hydrophobic comonomer. Finally, we note that M1 homopolymers are also responsive to Na₂SO₄ and could be readily salted‐out of an aqueous solution salt at a [Na₂SO₄] of 2.0 M giving a third trigger for controlling aqueous solubility. These copolymers represent examples of new multiresponsive materials and demonstrate the effectiveness of ROMP as a synthetic tool for the preparation of new and interesting materials. © 2014 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2015 , 53, 50–58     

Precise synthesis of poly(macromonomer)s containing sugars by repetitive ROMP and their attachments to poly(ethylene glycol): synthesis, TEM analysis and their properties as amphiphilic block fragments

Various poly(macromonomer)s (PMMs) have been prepared by a repeating ring opening metathesis polymerization (ROMP) technique using the well-defined molybdenum initiators of the type, [Mo(CHCMe(2)Ph)(NAr)(OR)(2)] with OR=OCMe(3), OCMeC(CF(3))(2); Ar=2,6-iPr(2)C(6)H(3), 2,6-Me(2)C(6)H(3). The synthetic strategy is based on the polymerization of norbornene and its derivatives affording di- and triblock side chains bearing sugars (mannose, galactose, glucose etc.), linked via O- (ester), and glycosidase resistant C- (isoxazoline) glycosides. The efficient placement of norbornene units on the side chain termini and their conversion into PMMs, facilitated by the Mo alkylidenes, proceeded in a living manner with the quantitative initiation. The methodology was applied to prepare poly(macromonomer)-graft-PEG [PEG: poly(ethylene glycol)], by the attachment of a pseudo phenol terminus on the PMM main chain to PEG-Ms(2) [MsO(CH(2)CH(2)O)(n)Ms, Ms=MeSO(2)] using a "grafting to" approach. Removal of the acetal protecting groups from the sugar coating of a variety of supramolecular structures including PMMs, linear amphiphilic block copolymers (ABC) and a PMM-graft-PEGby using trifluroacetic acid/water (9:1), and suspension in water, prompted the spontaneous formation of spherical architectures by self-assembly of the amphiphilic PMMs as observed by transmission electron microscopy (TEM). The ability to uptake the hydrophobic dye (Nile Red) into the micellar cores of a variety of amphiphilic polymeric fragments is a significant step towards the production of sugar-coated nanospheres for cell-targeting biomimetic applications.     

New ROMP Synthesis of Ferrocenyl Dendronized Polymers

First‐ and second‐generation Percec‐type dendronized ferrocenyl norbornene macromonomers containing, respectively, three and nine ferrocenyl termini are synthesized and polymerized by ring‐opening metathesis polymerization using Grubbs' third‐generation olefin metathesis catalyst with several monomer/catalyst feed ratios between 10 and 50. The rate of polymerization is highly dependent on the generation of the dendronized macromonomers, but all these ring‐opening metathesis polymerization reactions are controlled, and near‐quantitative monomer conversions are achieved. The numbers of ferrocenyl groups obtained are in agreement with the theoretical ones according to the cyclic voltammetry studies as determined using the Bard–Anson method.     

Synthesis of copolymers containing a spiro orthocarbonate moiety and evaluation of the volume change during their cationic crosslinking

Spiro orthocarbonate (SOC) monomers having either an exomethylene group {3,3‐dimethyl‐9‐methylene‐1,5,7,11‐tetraoxaspiro[5.5]undecane (ExoSOC)} or an allyl group {9‐allyl‐3,3‐dimethyl‐1,5,7,11‐tetraoxaspiro[5.5]undecane (AllylSOC)} were radically copolymerized with vinyl monomers at several feed ratios to obtain the corresponding copolymers having SOC moieties in the side chain. The obtained copolymers were crosslinked via the double ring‐opening polymerization of the SOC moieties by a treatment with boron trifluoride etherate. The volume changes during the crosslinking of the copolymers were evaluated by density measurements with a gas pycnometer. As the SOC moiety composition increased, the volume shrinkage during the crosslinking was suppressed, and that finally changed into volume expansion. The volume changes during the crosslinking of the copolymers from AllylSOC were slightly larger than those of the copolymers from ExoSOC. The higher volume expansions in the crosslinking of AllylSOC‐based copolymers were ascribable to the lower steric hindrance around the SOC moieties. © 2006 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 44: 7040–7053, 2006     

Living ROMP Synthesis and Redox Properties of Diblock Ferrocene/Cobalticenium Copolymers

Using the third‐generation Grubbs catalyst, the living ring‐opening metathesis polymerization of ferrocene/cobalticenium copolymers is conducted with theoretical numbers of 25 monomer units for each block, and their redox and electrochemical properties allow using the Bard–Anson electrochemical method to determine the number of metallocenyl units in each block.

     

Diblock Polyelectrolytic Copolymers Containing Cationic Iron and Cobalt Sandwich Complexes: Living ROMP Synthesis and Redox Properties

Diblock metallopolymer polyelectrolytes containing the two redox‐robust cationic sandwich units [CoCp′Cp]⁺ and [FeCp′(η⁶‐C₆Me₆)]⁺ (Cp = η⁵‐C₅H₅; Cp′ = η⁵‐C₅H₄‐) as hexafluorophosphate ([PF₆]⁻) salts are synthesized by ring‐opening metathesis polymerization using Grubbs' third generation catalyst. Their electrochemical properties show full chemical and electrochemical reversibilities allowing fine determination of the copolymer molecular weight using Bard–Anson's electrochemical method by cyclic voltammetry.

     

Influence of topology on the gelation behavior of coordination polymers prepared via ROMP of macrocyclic olefins

This work reports on the consequences of concatenation of two twin macrocycles on the gelation behavior of coordination polymers obtained via ring‐opening metathesis polymerization (ROMP) initiated by 2^nd generation Grubbs' catalyst. The influence of concatenation is evaluated by comparison with the behavior of a non‐interlocked model complex under the same reaction conditions. The suitability of the choice of the non‐interlocked model complex is discussed in terms of molecular structure and effective molarity (EM). It is found that concatenation has a primary role in the gelation process, resulting in lower critical gelation concentrations for the endotopic, interlocked complex compared with the exotopic, non‐interlocked one. © 2016 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2016 , 55, 1237–1242     

Synthesis of conjugated polymers containing anthracene moiety and their electro‐optical properties

Both fully conjugated polymer poly[2‐methoxy‐5‐(2‐ethylhexyloxy)‐1,4‐phenylene vinylene‐alt‐9,10‐anthrylene vinylene] [poly(MEHPV‐AV)] and conjugated/nonconjugated block copolymers poly(alkanedioxy‐2‐methoxy‐1,4‐phenylene‐1,2‐ethenylene‐9,10‐anthrylene‐1,2‐ehthenylene‐3‐methoxy‐1,4‐phenylene)[poly(BFMPx‐AV), (x = 4, 8, and 12)] were synthesized by Horner–Emmons reaction utilizing potassium tert‐butoxide. Of these synthesized polymers poly(BFMP4‐AV) and poly(BFMP8‐AV), which has four and six methylene groups as solubility spacer in the main chain exhibited liquid crystalline to isotropic transition in addition to the two first order transitions. Light‐emitting diode (LED)s made from the organic solvent soluble poly(BFMP12‐AV) as emitting layer showed blue shift in the emission spectrum compared to the one made from fully conjugated poly(MEHPV‐AV). Although poly(BFMP12‐AV) had higher barrier to the electron injection from cathode than poly(MEHPV‐AV), the luminance efficiency of LED made from poly(BFMP12‐AV) was about 25 times higher than the one made from poly(MEHPV‐AV), which had fully conjugated structure. LEDs fabricated by both poly(BFMP12‐AV) and poly(MEHPV‐AV) exhibited Stoke's shift in the range of 155 to 168 nm from the absorption maximum due to the excimer formation between the ground and excited state anthracene groups. © 2000 John Wiley & Sons, Inc. J Polym Sci A: Polym Chem 38: 3173–3180, 2000     

Synthesis,characterization, and thin‐film properties of 6‐oxoverdazyl polymers prepared by ring‐opening metathesis polymerization

Redox‐active 6‐oxoverdazyl polymers were synthesized via ring‐opening metathesis polymerization (ROMP) and their solution, bulk, and thin‐film properties investigated. Detailed studies of the ROMP method employed confirmed that stable radical polymers with controlled molecular weights and narrow molecular weight distributions (Ð < 1.2) were produced. Thermal gravimetric analysis of a representative example of the title polymers demonstrated stability up to 190 °C, while differential scanning calorimetry studies revealed a glass transition temperature of 152 °C. Comparison of the spectra of 6‐oxoverdazyl monomer 12 and polymer 13 , including FT‐IR, UV‐vis absorption, and electron paramagnetic resonance spectroscopy, was used to confirm the tolerance of the ROMP mechanism for the 6‐oxoverdazyl radical both qualitatively and quantitatively. Cyclic voltammetry studies demonstrated the ambipolar redox properties of polymer 13 (E_1/2,ox = 0.25 and E_1/2,red = ?1.35 V relative to ferrocene/ferrocenium), which were consistent with those of monomer 12 . The charge transport properties of thin films of polymer 13 were studied before and after a potential of 5 V was applied, revealing a drastic drop in the resistivity from 10⁶?10¹⁰ Ω m or more to 1.7 × 10⁴ Ω m and suggesting the potential usefulness of polymer 13 in bistable electronics. © 2016 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2016 , 54, 1803–1813     

Synthesis of polymers bearing 1,3‐benzoxazine moiety in the side chains from poly(allylamine) and their crosslinking behaviors

A polymer bearing 1,3‐benzoxazine moiety in the side chain was synthesized successfully from poly(allylamine) based on a stepwise strategy consisted of three steps: (1) treatment of poly(allylamine) with salicylaldehyde to convert the amino group in the side chain into the corresponding o‐(iminomethyl)phenol moiety, (2) reduction of the o‐(iminomethyl)phenol to obtain the corresponding o‐(aminomethyl)phenol moiety, and (3) formation of 1,3‐benzoxazine moiety by the reaction of the o‐(aminomethyl)phenol with formaldehyde. The content ratio of benzoxazine moieties and o‐(aminomethyl)phenol moieties in the polymer were tunable by varying amount of formaldehyde. The presence of o‐(aminomethyl)phenol moieties exhibited a significant promoting effect on the crosslinking reaction. © 2011 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem, 2011     

Synthesis of polynorbornene‐poly(tert‐butyl acrylate) nanoparticles with original morphologies by tandem ROMP and ATRP in microemulsion

Composite latex particles based on homopolymers and graft‐copolymers composed of polynorbornene (PNB) and poly(tert‐butyl acrylate) (PtBA) were synthesized in microemulsion conditions by simultaneous combination of two distinct methods of polymerization: Ring‐opening metathesis polymerization (ROMP) and atom transfer radical polymerization (ATRP). Only one commercial compound (first generation Grubbs catalyst) was used to initiate the ROMP of norbornene (NB) and activate the ATRP of tert‐butyl acrylate (tBA). Well‐defined nanoparticles with hydrodynamic diameters smaller than 50 nm were prepared with original morphologies depending on the monomer compositions, the type of combination (polymer blend or graft‐copolymer), and the conditions of microemulsion polymerizations. © 2011 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem, 2011     

Synthesis of norbornenes containing cationic mono‐ and di(cyclopentadienyliron)arene complexes and their ring‐opening metathesis polymerization

A number of classes of polynorbornenes containing cationic iron moieties within their side chains were prepared via ring‐opening metathesis polymerization with a ruthenium‐based catalyst. The iron‐containing polymers displayed excellent solubility in polar organic solvents. The weight‐average molecular weights of these polymeric materials were estimated to be in the range of 18,000–48,000. Thermogravimetric analysis of these polymers showed two distinct weight losses. The first weight loss was in the range of 204–260 °C and was due to the loss of the metallic moieties, whereas the second weight loss was observed at 368–512 °C and was due to the degradation of the polymer backbone. Cyclic voltammetry studies of the iron‐containing polymers showed that the 18 e^? cationic iron centers underwent a reduction to give the neutral 19 e^? complexes at half‐wave potential (E_1/2) = ?1.105 V. Photolysis of the metallated polymers led to the isolation of the norbornene polymers in very good yields. Differential scanning calorimetry studies showed a sharp increase in the glass‐transition temperatures up to 91 °C when rigid aromatic side chains were incorporated into the norbornene polymers. © 2006 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 44: 3053–3070, 2006     

One-Step Ring Opening Metathesis Block-Like Copolymers and their Compositional Analysis by a Novel Retardation Technique

Using a one-step synthetic route for block copolymers avoids the repeated addition of monomers to the polymerization mixture, which can easily lead to contamination and, therefore, to the unwanted termination of chain growth. For this purpose, monomers ( M1 – M5 ) with different steric hindrances and different propagation rates are explored. Copolymerization of M1 (propagating rapidly) with M2 (propagating slowly), M1 with M3 (propagating extremely slowly) and M4 (propagating rapidly) with M5 (propagating slowly) yielded diblock-like copolymers using Grubbs’ first ( G1 ) or third generation catalyst ( G3 ). The monomer consumption was followed by ¹H NMR spectroscopy, which revealed vastly different reactivity ratios for M1 and M2 . In the case of M1 and M3 , we observed the highest difference in reactivity ratios (r₁=324 and r₂=0.003) ever reported for a copolymerization method. A triblock-like copolymer was also synthesized using G3 by first allowing the consumption of the mixture of M1 and M2 and then adding M1 again. In addition, in order to measure the fast reaction rates of the G3 catalyst with M1 , we report a novel retardation technique based on an unusual reversible G3 Fischer-carbene to G3 benzylidene/alkylidene transformation.     

One‐Step Ring Opening Metathesis Block‐Like Copolymers and their Compositional Analysis by a Novel Retardation Technique

Using a one‐step synthetic route for block copolymers avoids the repeated addition of monomers to the polymerization mixture, which can easily lead to contamination and, therefore, to the unwanted termination of chain growth. For this purpose, monomers ( M1 – M5 ) with different steric hindrances and different propagation rates are explored. Copolymerization of M1 (propagating rapidly) with M2 (propagating slowly), M1 with M3 (propagating extremely slowly) and M4 (propagating rapidly) with M5 (propagating slowly) yielded diblock‐like copolymers using Grubbs’ first ( G1 ) or third generation catalyst ( G3 ). The monomer consumption was followed by ¹H NMR spectroscopy, which revealed vastly different reactivity ratios for M1 and M2 . In the case of M1 and M3 , we observed the highest difference in reactivity ratios (r₁=324 and r₂=0.003) ever reported for a copolymerization method. A triblock‐like copolymer was also synthesized using G3 by first allowing the consumption of the mixture of M1 and M2 and then adding M1 again. In addition, in order to measure the fast reaction rates of the G3 catalyst with M1 , we report a novel retardation technique based on an unusual reversible G3 Fischer‐carbene to G3 benzylidene/alkylidene transformation.     

Synthesis of amphiphilic homopolymers and their self‐assembly into acid‐responsive polymeric micelles

This contribution presents a strategy for preparing amphiphilic homopolymers as building blocks for self‐assembly into supramolecular nanostructures. The synthesis begins with norbornene monomers containing oligoethylene glycols on the side chains. Ring‐opening metathesis polymerization of the monomers and subsequent dihydroxylation afford water‐soluble dihydroxylated poly(norbornene)s (PNBs). Amphiphilic modifications of the hydrophilic PNBs can be achieved by reacting 1,2‐diols on the backbones with hydrophobic dodecanals to form acetal linkages. The self‐assembly of the resulting amphiphilic PNB homopolymers affords polymeric micelles whose morphologies can be tuned by breaking the acetal linkages under acidic conditions. © 2017 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2017 , 55, 3804–3808     

Cyclic polymers: Synthetic strategies and physical properties

Syntheses of cyclic polymers including cyclic homopolymers, cyclic block copolymers, sun‐shaped polymers, and tadpole polymers are discussed on the basis of a differentiation between synthetic methods and synthetic strategies (e.g., polycondensation, ring–ring equilibration, or ring‐expansion polymerization). Furthermore, all synthetic methods are classified as kinetically or thermodynamically controlled reactions. Characteristic properties of cyclic polymers such as smaller hydrodynamic volume, lower melt viscosities, and higher thermostabilities are compared to the properties of their linear counterparts. Furthermore, the nanophase separation of cyclic diblock copolymers is discussed. © 2009 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 48: 251–284, 2010