Synthesis of end‐functionalized polyethers by phosphazene base‐catalyzed ring‐opening polymerization of 1,2‐butylene oxide and glycidyl ether

For the living ring‐opening polymerization (ROP) of epoxy monomers, the catalytic activity of organic superbases, tert‐butylimino‐tris(dimethylamino)phosphorane, 1‐tert‐butyl‐2,2,4,4,4‐pentakis(dimethylamino)‐2Λ⁵,4Λ⁵‐catenadi(phosphazene), 2,8,9‐triisobutyl‐2,5,8,9‐tetraaza‐1‐phosphabicyclo[3.3.3]undecane, and 1‐tert‐butyl‐4,4,4‐tris(dimethylamino)‐2,2‐bis[tris(dimethylamino)phosphoranylidenamino]‐2Λ⁵,4Λ⁵‐catenadi(phosphazene) (t‐Bu‐P₄), was confirmed. Among these superbases, only t‐Bu‐P₄ showed catalytic activity for the ROP of 1,2‐butylene oxide (BO) to afford poly(1,2‐butylene oxide) (PBO) with predicted molecular weight and narrow molecular weight distribution. The results of the kinetic, post‐polymerization experiments, and MALDI‐TOF MS measurement revealed that the t‐Bu‐P₄‐catalyzed ROP of BO proceeded in a living manner in which the alcohol acted as the initiator. This alcohol/t‐Bu‐P₄ system was applicable to the glycidol derivatives, such as benzyl glycidyl ether (BnGE) and t‐butyl glycidyl ether, to afford well‐defined protected polyglycidols. The α‐functionalized polyethers could be obtained using different functionalized initiators, such as 4‐vinylbenzyl alcohol, 5‐hexen‐1‐ol, and 6‐azide‐1‐hexanol. In addition, the well‐defined cyclic‐PBO and PBnGE were successfully synthesized using the combination of t‐Bu‐P₄‐catalyzed ROP and click cyclization. © 2012 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem, 2012     

Functional polyesters prepared by polymerization of α‐allyl(valerolactone) and its copolymerization with ε‐caprolactone and δ‐valerolactone

We report the ring‐opening homopolymerization of α‐allyl(valerolactone), compound 2 , and its copolymerization with ε‐caprolactone and δ‐valerolactone using stannous(II) catalysis. Although the polymerization of substituted δ‐valerolactones has received little attention for the preparation of functional polyesters, we found that compound 2 may be incorporated in controllable amounts into copolymers with other lactones, or simply homopolymerized to give a highly functionalized, novel poly(valerolactone). The presence of the pendant allyl substituent had a substantial impact on the thermal properties of these materials relative to conventional polyesters prepared from lactones, and most of the polymers presented here are liquids at room temperature. Dihydroxylation of the pendant allyl groups gave polyesters with increased hydrophilicity that degraded more or less rapidly depending on their extent of functionality. © 2002 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 40: 1983–1990, 2002     

Formation of linear and cyclic polyoxetanes in the cationic ring‐opening polymerization of 3‐allyloxymethyl‐3‐ethyloxetane and subsequent postpolymerization modification of poly(3‐allyloxymethyl‐3‐ethyloxetane)

The synthesis of 3‐allyloxymethyl‐3‐ethyloxetane (AllylEHO) and its polymerization with BF₃ × Et₂O is described in this study. Size exclusion chromatography (SEC) and membrane osmometry are used for the determination of molecular weights of the obtained products, ranging from M_n,SEC = 41,500‐131,500 g/mol. ¹H NMR spectroscopy, SEC, as well as MALDI‐TOF MS reveal the formation of cyclic tetramer beside low, but detectable concentrations of larger cyclic oligomers as by‐products during the polymerization process. These results help to understand mechanistically why attempts for a controlled homopolymerization of AllylEHO fail and why a controlled homopolymerization of oxetanes has not been described so far in the literature. Additionally, the high versatility of allyl‐functional polyoxetane for postpolymerization modification is proven by thiol–ene reactions with 3‐mercaptopropionic acid and N‐acetyl‐L ‐cysteine methyl ester. © 2012 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem, 2013     

Selectivity in anionic and cationic ring‐opening polymerizations of tetramethyl‐1‐(3′‐trifluoromethylphenyl)‐1‐phenylcyclotrisiloxane and tetramethyl‐1‐[3′,5′‐bis(trifluoromethyl)phenyl]‐1‐phenylcyclotrisiloxane

Anionic and cationic ring‐opening polymerizations of two novel cyclotrisiloxanes, tetramethyl‐1‐(3′‐trifluoromethylphenyl)‐1‐phenylcyclotrisiloxane ( I ) and tetramethyl‐1‐[3′,5′‐bis(trifluoromethyl)phenyl]‐1‐phenylcyclotrisiloxane ( II ), are reported. Anionic ring‐opening polymerization of I or II leads to copolymers with highly regular microstructures. Copolymers obtained by cationic polymerizations of I or II , initiated by triflic acid, have less regular microstructures characteristic of chemoselective polymerization processes. The composition and microstructure of copolymers have been characterized by ¹H and ²⁹Si‐NMR, the molecular weight distributions by GPC, and the thermal properties by DSC and TGA. © 2004 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 42: 5235–5243, 2004     

Synthesis of block and end‐functionalized polyesters by triflimide‐catalyzed ring‐opening polymerization of ε‐caprolactone, 1,5‐dioxepan‐2‐one,and rac‐lactide

The ring‐opening polymerization (ROP) of cyclic esters, such as ε‐caprolactone, 1,5‐dioxepan‐2‐one, and racemic lactide using the combination of 3‐phenyl‐1‐propanol as the initiator and triflimide (HNTf₂) as the catalyst at room temperature with the [monomer]₀/[initiator]₀ ratio of 50/1 was investigated. The polymerizations homogeneously proceeded to afford poly(ε‐caprolactone) (PCL), poly(1,5‐dioxepan‐2‐one) (PDXO), and polylactide (PLA) with controlled molecular weights and narrow polydispersity indices. The molecular weight determined from an ¹H NMR analysis (PCL, M_n,NMR = 5380; PDXO, M_n,NMR = 5820; PLA, M_n,NMR = 6490) showed good agreement with the calculated values. The ¹H NMR and matrix‐assisted laser desorption ionization time‐of‐flight mass spectrometry analyses strongly indicated that the obtained compounds were the desired polyesters. The kinetic measurements confirmed the controlled/living nature for the HNTf₂‐catalyzed ROP of cyclic esters. A series of functional alcohols, such as propargyl alcohol, 6‐azido‐1‐hexanol, N‐(2‐hydroxyethyl)maleimide, 5‐hexen‐1‐ol, and 2‐hydroxyethyl methacrylate, successfully produced end‐functionalized polyesters. In addition, poly(ethylene glycol)‐block‐polyester, poly(δ‐valerolactone)‐block‐poly(ε‐caprolactone), and poly(ε‐caprolactone)‐block‐polylactide were synthesized using the HNTf₂‐catalyzed ROP. © 2013 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2013, 51, 2455–2463     

Ring‐Opening and polymerization of 1‐[2′‐(heptaphenylcyclotetrasiloxanyl)ethyl]‐1,3,3,5,5‐pentamethylcyclotrisiloxane

1‐[2′‐(Heptaphenylcyclotetrasiloxanyl)ethyl]‐1,3,3,5,5‐pentamethylcyclotetrasiloxane ( II ) was prepared from 1‐[2′‐(methyldichlorosilyl)ethyl]‐1,3,3,5,5,7,7‐heptaphenylcyclotetrasiloxane ( I ) and tetramethyldisiloxane‐1,3‐diol. Acid‐catalyzed ring‐opening of II in the presence of tetramethyldisiloxane gave 1,9‐dihydrido‐5‐[2′‐(heptaphenylcyclotetrasiloxanyl)ethyl]nonamethylpentasiloxane ( III ) and 1,9‐dihydrido‐3‐[2′‐(heptaphenylcyclotetrasiloxanyl)ethyl]nonamethylpentasiloxane ( IV ). Both acid‐ and base‐catalyzed ring‐opening polymerization of II gives highly viscous, transparent polymers. The structures of I – IV and polymers were determined by UV, IR, ¹H, ¹³C, and ²⁹Si NMR spectroscopy. In addition, molecular weights obtained by GPC and NMR end group analysis were confirmed with mass spectrometry. On the basis of ²⁹Si NMR spectroscopy, the polymers appear to result exclusively from ring‐opening of the cyclotrisiloxane ring. No evidence for ring‐opening of the cyclotetrasiloxane ring was observed. Polymer properties were determined by DSC and TGA. © 2005 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 44: 137–146, 2006     

Incorporation of ketone groups into poly(4‐hydroxystyrene)s main chain by radical copolymerization of 2,2‐diphenyl‐4‐methylene‐1,3‐dioxorane with O‐protected hydroxystyrenes and their photodegradable behavior

Here we report the incorporation of ketone groups into poly(4‐hydroxystyrene)s main chain by radical copolymerization of O‐protected hydroxystyrenes such as 4‐ethoxyethoxystyrene and 4‐acetoxystyrene with 2,2‐diphenyl‐4‐methylene‐1,3‐dioxorane (DPMD) followed by removal of the protective groups and the photodegradable behavior of obtained copolymers. The copolymerization of O‐protected hydroxystyrenes with DPMD gave the corresponding copolymers bearing DMPD‐derived ketone groups in the main chain, of which content could be controlled by changing monomer feed ratio. The ethoxyethyl and acetyl groups of the obtained copolymers were completely removed under acidic and basic conditions, respectively, to afford poly(4‐hydroxystyrene)s having ketone moieties in the main chain. The molecular weights of these copolymers decreased under photoirradiation due to the Norrish‐type reactions of the ketone groups distributed in the main chain. These results demonstrate that poly(4‐hydroxystyrene)s having ketone groups in the main chain possess good photo‐scissibility. © 2011 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem, 2011     

The Surface Modification of Hydroxyapatite Nanoparticles by the Ring Opening Polymerization of γ‐Benzyl‐L‐glutamate N‐carboxyanhydride

The surface modification of hydroxyapatite (HA) nanoparticles by the ring opening polymerization (ROP) of γ‐benzyl‐L ‐glutamate N‐carboxyanhydride (BLG‐NCA) was proposed to prepare the poly(γ‐benzyl‐L ‐glutamate) (PBLG)‐grafted HA nanoparticles (PBLG‐g‐HA) for the first time. HA nanoparticles were firstly treated by 3‐aminopropylthriethoxysilane (APS) and then the terminal amino groups of the modified HA particles initiated the ROP of BLG‐NCA to obtain PBLG‐g‐HA. The process was monitored by XPS and FT‐IR. The surface grafting amounts of PBLG on HA ranging from 12.1 to 43.1% were characterized by thermal gravimetric analysis (TGA). The powder X‐ray diffraction (XRD) analysis confirmed that the ROP only underwent on the surface of HA nanoparticles without changing its bulk properties. The SEM measurement showed that the PBLG‐g‐HA hybrid could form an interpenetrating net structure in the self‐assembly process. The PBLG‐g‐HA hybrid could maintain higher colloid stability than the pure HA nanoparticles. The in vitro cell cultures suggested the cell adhesion ability of PBLG‐g‐HA was much higher than that of pure HA.

     

Cationic polymerization of seven‐membered cyclic monothiocarbonate 1,3‐dioxepan‐2‐thione

The cationic ring‐opening polymerization of a seven‐membered cyclic monothiocarbonate, 1,3‐dioxepan‐2‐thione, produced a soluble polymer through the selective isomerization of thiocarbonyl to a carbonyl group {? [SC(C?O)O(CH₂)₄]_n? }. The molecular weights of the polymer could be controlled by the feed ratio of the monomer to the initiators or the conversion of the monomer during the polymerization, although some termination reactions occurred after the complete consumption of the monomer. © 2005 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 43: 1014–1018, 2005     

Functional 1,3‐benzoxazine bearing 4‐pyridyl group: Synthesis and thermally induced polymerization behavior

1,3‐benzoxazine 1 , bearing 4‐pyridyl moiety on the nitrogen atom, was synthesized from p‐cresol, 4‐aminopyridine, and paraformaldehyde. The efficient synthesis was achieved by adding acetic acid to suppress the strong basicity caused by the presence of 4‐aminopyridine derivatives. Upon heating 1 at 180 °C, it underwent the thermally induced ring‐opening polymerization. The resulting polymer was composed of two types of repeating unit, i.e., (1) Mannich‐type one (‐phenol‐CH₂‐NR‐CH₂‐) that can be expected from the general ring‐opening polymerization of conventional benzoxazines and (2) a typical phenolic resin‐type one (‐phenol‐CH₂‐phenol‐) induced by release of 4‐aminopyridine and paraformaldehyde (unit B). Another structural feature of the polymer was that it possessed a benzoxazine moiety at the chain end. © 2013 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2014 , 52, 410–416     

Poly(hydroxyisobutyrate) by ring‐opening polymerizations of 5,5‐dimethyl‐1,3,2‐dioxithiolan‐4‐one‐2‐oxide

α‐Hydroxyisobutyric acid anhydrosulfate HiBAS (5,5‐dimethyl‐1,3,2‐dioxithiolan‐4‐one‐2‐oxide) was polymerized under various reaction conditions and the solid reaction products were characterized by ¹H NMR spectroscopy, MALDI‐TOF mass spectrometry (MT m.s.), fast atom bombardment mass spectrometry (FAB m.s.), viscosity, and SEC measurements. Thermal polymerizations at 100 °C mainly yielded cyclic oligo polyesters presumably resulting from a zwitterionic polymerization. Cycles were also detected when pyridine was used as catalyst at 20 °C. When triethylamine was used as catalyst traces of H₂O played the role of initiators. Benzyl alcohol initiated the polymerization of HiBAS at 100 °C and yielded a polyester terminated by one benzylester and one OH endgroup. The SEC measurements indicated that all samples possess relatively low molar masses with number–average molecular weights ≤ 10,000 Da (in contrast to the literature data). © 2008 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 46: 6229–6237, 2008     

Polymerization of (L,L)‐lactide and copolymerization with ϵ‐caprolactone initiated by dibutyltin dimethoxide in supercritical carbon dioxide

Ring‐opening polymerization (ROP) of (L,L)‐lactide (LA) has been initiated by dibutyltin dimethoxide in supercritical carbon dioxide (sc CO₂). Polymerization is controlled and proceeds at quasi the same rate as in toluene, which indicates that the reactivity of the propagating species is not impaired by parasitic carbonation reaction. Random copolymerization of LA with ?‐caprolactone (CL) has also been studied in sc CO₂, and the reactivity ratios have been determined as 5.8 ± 0.5 for LA and 0.7 ± 0.25 for CL. These values have to be compared to 0.7 ± 0.25 for LA and 0.15 ± 0.05 for CL in toluene. Good control on ROP of CL and LA in sc CO₂ has been confirmed by the successful synthesis of diblock copolymers by sequential polymerization of CL and LA. © 2005 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 43: 2777‐2789, 2005     

Hierarchical Self‐Assembly of Double‐Crystalline Poly(ferrocenyldimethylsilane)‐block‐poly(2‐iso‐propyl‐2‐oxazoline) (PFDMS‐b‐PiPrOx) Block Copolymers

The step‐wise solution self‐assembly of double crystalline organometallic poly(ferrocenyldimethylsilane)‐block‐poly(2‐iso‐propyl‐2‐oxazoline) (PFDMS‐b‐PiPrOx) diblock copolymers is demonstrated. Two block copolymers are obtained by copper‐catalyzed azide‐alkyne cycloaddition (CuAAC), featuring PFDMS/PiPrOx weight fractions of 46/54 (PFDMS₃₀‐b‐PiPrOx₇₅) and 30/70 (PFDMS₃₀‐b‐PiPrOx₁₅₅). Nonsolvent induced crystallization of PFDMS in acetone leads in both cases to cylindrical micelles with a PFDMS core. Afterward, the structures are transferred into water for sequential temperature‐induced crystallization of the PiPrOx corona, leading to hierarchical double crystalline superstructures, which are investigated using scanning electron microscopy, wide angle X‐ray scattering, and differential scanning calorimetry.

     

Ring‐opening polymerization of 1,3‐benzoxazines by p‐toluenesulfonates as thermally latent initiators

p‐Toluenesulfonic acid (TsOH) and several alkyl p‐toluenesulfonates, that is, methyl p‐toluenesulfonate (TsOMe), cyclohexyl p‐toluenesulfonate (TsOCH), and neopentyl p‐toluenesulfonate (TsONP), were evaluated as initiators for the ring‐opening polymerization of benzoxazines. TsOH and TsOMe were highly efficient initiators that induced the polymerization at 60 and 80 °C, respectively. In contrast, TsOCH and TsONP did not initiate the polymerization below 100 °C, while they induced the polymerization at elevated temperatures, 120 and 150 °C, respectively. When TsOCH was used as an initiator, the corresponding polymerization rate was comparable to that observed for the polymerization with using TsOH as an initiator. These results suggested that neutral TsOCH and TsONP can be regarded as “thermally latent initiators,” which underwent the thermal dissociation at the elevated temperatures to generate the corresponding alkyl cations and/or TsOH as the initiators of the polymerization. © 2011 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem, 2011     

Radical Ring‐Opening Polymerization Behavior of 1,1‐Dicyano‐2‐Vinylcyclopropane and Its Copolymerization with 1‐Cyano‐1‐Ester‐2‐Vinylcyclopropane

Radical ring‐opening polymerization of 1,1‐dicyano‐2‐vinylcyclopropane 1 was performed in benzonitrile to find the corresponding homopolymer 2 soluble in organic solvents was successfully obtained while that in other solvents gave crosslinked and thus insoluble homopolymer. In addition, 1 underwent radical copolymerization with 1‐cyano‐1‐ester‐2‐vinylcyclopropanes 3 and 4 to afford the corresponding copolymers 7 and 8 . By increasing the content of the 1 ‐derived unit in the resulting copolymers, the solubility of the copolymers in organic solvents became lower and the residual weights at 600 °C and their glass transition temperatures became higher. © 2019 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2019, 57, 1723–1729     

Synthesis of telechelic anthraquinone‐functionalized polybutadiene via ROMP and study of its photo‐oxidation and UV crosslinking behaviors

Telechelic anthraquinone‐functionalized polybutadiene (AQ‐PB‐AQ) was synthesized by ring opening metathesis polymerization to achieve homogeneous dispersion of AQ groups in the polymer matrix. It was observed that the AQ end groups act as a sensitizing group resulting in photo‐induced crosslinking and oxidation reaction at the olefin groups in the PB. The process was confirmed by comparing the polymer's mass loss and Fourier transform infrared (FTIR) spectra with those of telechelic diacetoxy‐functionalized PB (AcO‐PB‐OAc) which did not show any difference before and after ultraviolet irradiation. Homogeneity of the AQ groups in PB matrix results in rapid crosslinking of PB in a short period of time (<4 min) while a simple blend of AQ methyl ester in AcO‐PB‐OAc matrix did not show such behavior. Photo‐oxidative reaction has concurrently occurred during the crosslinking reaction. Generation of  OH,  OOH, and carbonyl groups in the matrix during the photo‐oxidation was verified by FTIR, elemental analysis, and water contact angle measurements. A plausible mechanism for the process was proposed in which the photo‐sensitized AQ groups abstract hydrogen from the PB chain to yield reactive radical species, initiating oxidative crosslinking, and degradation of PB or reduction of AQ to hydroanthraquinone species. © 2018 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2018 , 56, 1249–1258     

From Syndiotactic Homopolymers to Chemically Tunable Alternating Copolymers: Highly Active Yttrium Complexes for Stereoselective Ring‐Opening Polymerization of β‐Malolactonates

Alternating copolymers constitute an attractive class of materials. It was shown previously that highly alternated poly(β‐hydroxyalkanoate)s (PHAs) can be prepared by ring‐opening polymerization (ROP) of mixtures of two different enantiomerically pure 4‐alkyl‐β‐propiolactones. However, the approach could not be extended to PHAs with chemically tunable functional groups, which is highly desirable to access original advanced materials. Reported herein is the first highly syndioselective and controlled ROP of racemic allyl and benzyl β‐malolactonates (MLA^R; R=allyl, benzyl) using an yttrium complex supported by a tetradentate dichloro‐substituted bis(phenolate) ligand. This highly active catalyst allows the nearly perfect alternating copolymerization of MLA^Allyl and MLA^Benzyl. Hydrogenolysis of the benzyloxycarbonyl or functionalization of the allyl pendant groups opens a route towards a new class of functional alternating copolymers.