Cationic polymerization of cyclocarbonates

Trimethylenecarbonate (TMC) and neopentane diol carbonate (NPC) were polymerized with two groups of initiators, proton and carbenium ion donors or Lewis acids. Initiation with methyltriflate, triflic acid or triethyloxonium tetrafluoroborate in solution gave satisfactory yields (up to 90%) but only low molecular weights (M_n < 5000), due to rapid back-biting degradation. IR- and NMR-spectroscopy demonstrate that the propagation steps involve alkylation of the carbonyl oxygen and cleavage of the alkyl-0 bond by analogy with lactones. Whereas borontribromide and trichloride form solid complexes with NPC or TMC, but do not initiate a polymerization, boron trifluoride is a good initiator. High yields (up to 99,5%) and high molecular weights (M_w > 10⁵) were obtained. However, in analogy to triflic acid initiated polymerizations all polycarbonates contain ether groups. The molar fraction of the ether groups increases with the reaction temperature. High molecular-weight polycarbonates containing ether groups were also obtained with other strong Lewis acids such as SnCl₄, SnBr₄ and TiCl₄. In contrast, weak Lewis acids such as Bu₂SnBr₂ Bu₃SnOMe and Sn(II)2-ethylhexanoate yield polycarbonates free of ether groups. This finding and the NMR-spectroscopically identified endgroups suggest that these weak Lewis acids initiate an insertion mechanism.     

Stable,Hydroxyl Functional Polycarbonates With Glycerol Side Chains Synthesized From CO2 and Isopropylidene(glyceryl glycidyl ether)

A series of functional polycarbonates, poly((isopropylidene glyceryl glycidyl ether)‐co‐(glycidyl methyl ether) carbonate) (P((IGG‐co‐GME) C)) random copolymers with different fractions of 1,2‐isopropylidene glyceryl glycidyl ether (IGG) units, is synthesized. After acidic hydrolysis of the acetal protecting groups, a new type of functional polycarbonate prepared directly from CO₂ and glycerol is obtained, namely poly((glyceryl glycerol)‐co‐(glycidyl methyl ether) carbonate) (P((GG‐co‐GME) C)). All hydroxyl functional samples exhibit monomodal molecular weight distributions with PDIs between 2.5 and 3.3 and M _n between 12 000 and 25 000 g mol⁻¹. Thermal properties reflect the amorphous structure of the polymers. The materials are stable in bulk and solution.     

Synthesis and Modification of Functional Polycarbonates with Pendant Allyl Groups

Functional aliphatic polycarbonates with pendant allyl groups were synthesised by copolymerization of carbon dioxide and allyl glycidyl ether (AGE) in the presence of a catalyst system based on ZnEt₂ and pyrogallol at a molar ratio 2 : 1. The functionality of some polycarbonates was reduced by replacing a part of allyl ether with saturated glycidyl ether, i.e., butyl glycidyl ether (BGE) or isopropyl glycidyl ether (IGE). Polycarbonates obtained by the copolymerization of AGE and CO₂ or by the terpolymerization of AGE, IGE and CO₂ were oxidized with m‐chloroperbenzoic acid to their respective poly(epoxycarbonate)s. The influence of the AGE/ΣGE ratio in the polycarbonates, the polymer concentration in the reaction solution and the duration of the reaction on the conversion of allyl groups into glycidyl ones was examined. A tendency to gelation of the initial and oxidized polycarbonates during storage was observed. The initial polycarbonates and their oxidized forms were degraded in aqueous buffer of pH = 7.4 at 37°C. The course of hydrolytic degradation was monitored by the determination of mass loss.     

Biodegradable Polycarbonate Synthesis by Copolymerization of Carbon Dioxide with Epoxides Using a Heterogeneous Zinc Complex

As a means for the chemical fixation of carbon dioxide and the synthesis of biodegradable polycarbonates, copolymerizations of carbon dioxide with various epoxides such as cyclohexene oxide (CHO), cyclopetene oxide, 4-vinyl-1-cyclohexene-1,2epoxide, phenyl glycidyl ether, allyl glycidyl ether, propylene oxide, butene oxide, hexene oxide, octene oxide, and 1-chloro-2,3-epoxypropane were investigated in the presence of a double metal cyanide catalyst (DMC). The DMC catalyst was prepared by reacting K₃Co(CN)₆ with ZnCl₂, together with tertiary butyl alcohol and poly(tetramethylene ether glycol) as complexing reagents and was characterized by various spectroscopic methods. The DMC catalyst showed high activity (526.2 g-polymer/g-Zn atom) for CHO/CO₂ (P_CO2 = 140 psi) copolymerization at 80 °C, to yield biodegradable aliphatic polycarbonates of narrow polydispersity (M_w/M_n = 1.67) and moderate molecular weight (M_n = 8900). The DMC catalyst also showed high activities with different CO₂ reactivities for other epoxides to yield various aliphatic polycarbonates with narrow polydispersity.     

Studies on microwave-assisted ring-opening polymerization and property of poly(9-phenyl-2,4,8,10-tetraoxaspiro-[5,5]undcane-3-one)

Poly(9-phenyl-2,4,8,10-tetraoxaspiro-[5,5]undcane-3-one)(PPTC) was synthesized by the microwave-assisted ring-opening polymerization(MROP) of a six-membered cyclic carbonate monomer 9-phenyl-2,4,8,10-tetraoxaspiro-[5,5]undcane-3-one(PTC) with tin(Ⅱ) 2-ethylhexanoate(Sn(Oct)_2) or aluminum isopropoxide(Al(O~iPr)_3) as the catalysts. The obtained polycarbonates were further reduced by apalladium/carbonate catalyst(10% Pd/C) to afford partly deprotected polycarbonates containing hydroxyl groups(HPPTC). These two types of polycarbonates were characterized by ~1H-NMR, Fourier transform infrared spectroscopy(FTIR), UV, gel permeation chromatography(GPC), differential scanning calorimetry(DSC), and automatic contact-angle measurements. The influence of the feed molar ratio of monomer-to-catalyst, the microwave irradiation power and the reaction time on the polymerization was also studied. The experimental results showed that HPPTC possessed significantly higher hydrophilicity and water absorption rate than PPTC.     

Polylactones. 16. Cationic Polymerization of Trimethylene Carbonate and Other Cyclic Carbonates

1,3-Dioxanone-2 (trimethylene carbonate) was polymerized by use of methyl triflate or triethyloxonium fluoborate under various reaction conditions. Chloroform, 1,2-dichloroethane, and nitrobenzene were used as solvents; the temperature was varied between 25 and 50°C; and the monomer/initiator ratio between 50 and 400. However, inherent viscosities above 0.29 dL/g ( M _n > 6000) were never obtained, owing to side reactions such as backbiting and formation of ether groups. IR and ¹H-NMR spectroscopy revealed that the polymerization mechanism agrees with that of the cationic polymerization of lactones in that propagation involves cleavage of the alkyl-oxygen bond. The active cationic chain end and the dead methylcarbonate end groups were identified by means of ¹H-NMR spectra. A reaction mechanism for the formation of ether groups is discussed. Furthermore, ¹H-NMR spectroscopy indicated that ethylene carbonate and biphenyl-2,2′-carbonate do not react with methyl triflate at 20, 60, or even 100°C.     

Hyperbranched aryl polycarbonates derived from A2B monomers versus AB2 monomers

Hyperbranched aryl polycarbonates were prepared via the polymerizations of A₂B and AB₂ monomers, which involved the condensation of chloroformate (A) functionalities with tert‐butyldimethylsilyl‐protected phenols (B), facilitated by reactions with silver fluoride. The polymerization of the A₂B monomer gave hyperbranched polycarbonates bearing fluoroformate chain ends, which were hydrolyzed to phenolic chain‐end moieties and further elaborated to tert‐butyldimethylsilyl ether groups. The polymerization of the AB₂ monomer gave tert‐butyldimethylsilyl ether‐terminated hyperbranched polycarbonates. The polymerizations were conducted at 23–70 °C in 20% acetonitrile/tetrahydrofuran in the presence of a stoichiometric excess of silver fluoride for 20–40 h to afford hyperbranched polycarbonates with weight‐average molecular weights exceeding 100,000 Da and polydispersity indices of typically 2–3. The degrees of branching were determined by a reductive degradation procedure followed by high‐performance liquid chromatography. Alternatively, the degrees of branching were measurable by solution‐state ¹H NMR analyses and agreed with the statistical 50% branching expected for the polymerization of A₂B and AB₂ monomers not experiencing constructive or destructive electronic effects on the reactivity of the multiple functional groups. © 2002 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 40: 823–835, 2002; DOI 10.1002/pola.10167     

Synthesis and characterization of novel aliphatic polycarbonates

A new six‐membered cyclic carbonate monomer, 5‐benzyloxy‐trimethylene carbonate, was synthesized from 2‐benzyloxy‐1,3‐propanediol, and the corresponding polycarbonate, poly(5‐benzyloxy‐trimethylene carbonate) (PBTMC), was further synthesized by ring‐opening polymerization in bulk at 150 °C using aluminum isobutoxide [Al(OⁱBu)₃], aluminum isopropoxide, or stannous octanoate as an initiator. The results showed that a higher molecular weight polycarbonate could be obtained in the case of Al(OⁱBu)_3. The protecting benzyl group was removed subsequently by catalytic hydrogenation to give a polycarbonate containing a pendant hydroxyl group (PHTMC). The polycarbonates obtained were characterized by Fourier transform infrared spectroscopy, ¹H NMR,¹³C NMR, gel permeation chromatography, and DSC. NMR results of PBTMC offered no evidence for decarboxylation occurring during the propagation. The pendant hydroxyl group in PHTMC resulted in an enhancement of the hydrophilicity of the polycarbonate. © 2001 John Wiley & Sons, Inc. J Polym Sci Part A: Polym Chem 40: 70–75, 2002     

Polymers of carbonic acid. XVII. Polymerization of cyclobis(tetramethylene carbonate) by means of BuSnCl3 and Sn(II) 2-ethylhexanoate

Dimeric cyclotetramethylene carbonate (TeMC)₂ was polymerized in bulk at 185°C. Either nBuSnCl₃ or Sn(II)2-ethylhexanoate (SnOct₂) were used as catalysts. SnOct₂ proved to be somewhat less reactive, but high yields (up to 93%) and high viscosities (ν_inh up to 0.85 dL/g) were obtained with both catalysts. Viscosity-average molecular weights (M_v) in the range of 50–75 × 10³ were determined. The isolated crystalline poly(tetramethylene carbonate)s were characterized by IR, ¹H- and ¹³C-NMR spectra, DSC measurements and WAXD powder pattern. CH₂OH and octoate end groups were detected by means of ¹H-NMR spectroscopy when SnOct₂ was used as initiator, but ether groups were absent. DSC measurements revealed that poly(tetramethylene carbonate) is a slowly crystallizing polymer with a degree of crystallinity below 50% and a melting temperature in the range of 64–69°C depending on the molecular weight. Thermogravimetric analyses proved that polyTeMC decomposes completely between 240 and 340°C without leaving a residue. CO₂ and tetrahydrofuran were the main degradation products. © 1996 John Wiley & Sons, Inc.     

Allyl ethers as combined plasticizing and crosslinkable side groups in polycarbonate‐based polymer electrolytes for solid‐state Li batteries

Allyl ether‐functional polycarbonates, synthesized by organocatalytic ring‐opening polymerization of the six‐membered cyclic carbonate monomer 2‐allyloxymethyl‐2‐ethyltrimethylene carbonate, were used to prepare non‐polyether polymer electrolytes. UV‐crosslinking of the allyl side groups provided mechanically stable electrolytes with improved molecular flexibility—T_g below ?20 °C—and higher ionic conductivity—up to 4.3 × 10^?7 S/cm at 25 °C and 5.2 × 10^?6 S/cm at 60 °C—due to the plasticizing properties of the allyl ether side groups. The electrolyte function was additionally demonstrated in thin‐film Li battery cells. © 2016 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2016 , 54, 2128–2135     

Bifunctional imidodiphosphoric acid‐catalyzed controlled/living ring‐opening polymerization of trimethylene carbonate resulting block, α,ω‐dihydroxy telechelic,and star‐shaped polycarbonates

The ring‐opening polymerization (ROP) of trimethylene carbonate (TMC) using imidodiphosphoric acid (IDPA) as the organocatalyst and benzyl alcohol (BnOH) as the initiator has been investigated. The polymerization proceeded without decarboxylation to afford poly(trimethylene carbonate) (PTMiC) with controlled molecular weight and narrow polydispersity. ¹H NMR, SEC, and MALDI‐TOF MS measurements of the obtained PTMC clearly indicated the quantitative incorporation of the initiator at the chain end. The controlled/living nature for the IDPA‐catalyzed ROP of TMC was confirmed by the kinetic and chain extension experiments. A bifunctional activation mechanism was proposed for IDPA catalysis based on NMR and FTIR studies. Additionally, 1,3‐propanediol, 1,1,1‐trimethylolpropane, and pentaerythritol were used as di‐ol, tri‐, and tetra‐ol initiators, producing the telechelic or star‐shaped polycarbonates with narrow polydispersity indices. The well‐defined diblock copolymers, poly(trimethylene carbonate)‐block‐poly(δ‐valerolactone) and poly(trimethylene carbonate)‐block‐poly(ε‐caprolactone), have been successfully synthesized by using the IDPA catalysis system. © 2013 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2014 , 52, 1009–1019     

Sulfur containing polymers.: Aromatic polydithiocarbonates and polythiocarbonates: synthesis and thermal properties

New polydithiocarbonates and polythiocarbonates were obtained by interfacial polymerization of bis(4-mercaptophenyl)methane, bis(4-mercaptophenyl)ether and bis(4-mercaptophenyl)sulfide with phosgene, bisphenol A bischloroformate and bisphenol A polycarbonate oligomers (-OH/-O-CO-Cl terminated). Polymerization process was carried out under interfacial conditions using a phase-transfer catalyst, as earlier described for the synthesis of polydithiocarbonates and polythiocarbonates from 2,2-bis(4-mercaptophenyl)propane. The structures of the polymers were examined by IR and NMR spectroscopies; their thermal properties were investigated by thermogravimetric analysis and differential scanning calorimetry. In particular, the effect of the substitution of one or both the ethereal oxygen atoms of the carbonate group by sulfur has been analyzed by comparing the T_g values and the ability to crystallize of the sulfur containing polymers with those of the corresponding polycarbonates.     

Biodegradable polymers based on renewable resources. IX. Synthesis and degradation behavior of polycarbonates based on 1,4:3,6‐dianhydrohexitols and tartaric acid derivatives with pendant functional groups

Novel polycarbonates, with pendant functional groups, based on 1,4:3,6‐dianhydrohexitols and L ‐tartaric acid derivatives were synthesized. Solution polycondensations of 1,4:3,6‐dianhydro‐bis‐O‐(p‐nitrophenoxycarbonyl)hexitols and 2,3‐di‐O‐methyl‐L ‐threitol or 2,3‐O‐isopropylidene‐L ‐threitol afforded polycarbonates having pendant methoxy or isopropylidene groups, respectively, with number average molecular weight (M_n) values up to 3.6₁ × 10⁴. Subsequent acid‐catalyzed deprotection of isopropylidene groups gave well‐defined polycarbonates having pendant hydroxyl groups regularly distributed along the polymer chain. Differential scanning calorimetry (DSC) demonstrated that all the polycarbonates were amorphous with glass transition temperatures ranging from 57 to 98 °C. Degradability of the polycarbonates was assessed by hydrolysis test in phosphate buffer solution at 37 °C and by biochemical oxygen demand (BOD) measurements in an activated sludge at 25 °C. In both tests, the polycarbonates with pendant hydroxyl groups were degraded much faster than the polycarbonates with pendant methoxy and isopropylidene groups. It is noteworthy that degradation of the polycarbonates with pendant hydroxyl groups was remarkably fast. They were completely degraded within only 150 min in a phosphate buffer solution and their BOD‐biodegradability reached nearly 70% in an activated sludge after 28 days. The degradation behavior of the polycarbonates is discussed in terms of their chemical and physical properties. © 2005 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 43: 3909–3919, 2005     

Synthesis and characterization of polycarbonates based on bisphenol S by melt transesterification

Several sulfone-containing polycarbonates, having inherent viscosity 0.25–0.30 dL g⁻¹ in N,N-dimethylformamide (DMF), were prepared by melt polycondensation of diphenyl carbonate (DPC) with various aromatic and aliphatic diols, in the presence of zinc acetate as transesterification catalyst. The polycarbonates were examined with IR spectra, inherent viscosity, solubility, tensile strength, contact angle, DSC and TGA. Almost all polymers were soluble in DMF, pyridine, N-methyl pyrrolidinone (NMP), THF, phenol and dimethylsulfoxide (DMSO), partially soluble in nitrobenzene, but insoluble in acetone. Polycarbonate with introduced ether linkages leads to enhanced flexibility and elongation strength. The contact angle of the polycarbonate based on bisphenol S was found in the range 42–80°, smaller than that of polycarbonates based on bisphenol AF and bisphenol A. The wettability of polycarbonate films based on bisphenol S remarkably increased with increasing oxyethylene unit in polymer chain. The smaller values of T_d of PC-3-PC-7 than of PC-1 is attributed to the flexible ether linkage. The thermal stability of a brominated aromatic polycarbonate (PC-2) is less than that of the unbrominated one (PC-1). The brominated aromatic polycarbonate (PC-2) has good flame retardency, as indicated by the large limiting oxygen index 56. © 1997 John Wiley & Sons, Inc. J Polym Sci A: Polym Chem 35 : 2453–2460, 1997     

Metal-free synthesis of reactive oligomers by ring-opening oligomerization of glycidyl phenyl ether initiated with tetra-n-butylammonium fluoride in the presence of various protic compounds

Metal-free ring-opening oligomerizations of glycidyl phenyl ether (GPE) were performed with tetra-n-butylammonium fluoride (n-Bu₄NF) as an initiator in the presence of protic compounds (RHs) as chain transfer agents (CTAs). The RHs having pKa between 4.66 and 15.5 enabled to serve as the CTA in this oligomerization system, leading to reactive oligomers with relatively controlled molecular weights having narrow molecular weight distributions bearing functional groups such as alkene, benzyl ether, alkyne, ester and methacrylate groups at initiating end.     

Anionic bulk oligomerization of ethylene and propylene carbonate initiated by bisphenol‐A/base systems

When the bulk oligomerization of 1,3‐dioxolan‐2‐one (ethylene carbonate, EC) and 4‐methyl‐1,3‐dioxolan‐2‐one (propylene carbonate, PC) with the 2,2‐bis(4‐hydroxyphenyl)propane (bisphenol‐A, BPA)/base system (bases such as KHCO₃, K₂CO₃, KOH, Li₂CO₃, and t‐BuOK) was investigated at elevated temperature, significant differences were observed. Oligomerization of EC initiated by BPA/base readily takes place, but the oligomerization of PC is inhibited. The very first propylene carbonate/propylene oxide unit readily forms a phenolic ether bond with the functional groups of BPA phenolate, but the addition of the second monomer unit is rather slow. The oligomerization of EC yields symmetrical oligo(ethylene oxide) side chains. According to IR studies the oligomeric chains formed from PC with BPA contain not only ether but also carbonate bonds. The in situ step oligomerization of the BPA dipropoxylate was also identified by SEC, and a possible reaction mechanism is proposed. © 1999 John Wiley & Sons, Inc. J Polym Sci A: Polym Chem 37: 545–550, 1999     

Synthesis of polycarbonates by a silicon-assisted alkoxy/carbonylimidazolide coupling reaction

The investigation of a silicon-mediated coupling reaction between hydroxyl and carbonylimidazolide functional groups in the preparation of carbonate linkages is described. Application of this reaction to the formation of aliphatic polycarbonates was accomplished by the polymerization of an AB monomer unit, which was composed of 1,4-cyclohexanediol, where one of the hydroxyl groups was protected as a dimethylphenylsilyl ether and the other carried the carbonylimidazolide functionality. Reaction of this monomer with cesium fluoride removed the silicon protecting group and the resulting alkoxy anion promoted polymerization. Poly(1,4-cyclohexanecarbonate)s with typical molecular weights of M_w = 20,000 and M_n = 7300 a.m.u. (from GPC based upon polystyrene standards) were prepared in ca. 65% yield. The polymer showed a glass transition temperature at 138°C by DSC. TGA gave 85% mass loss between 275 and 350°C. © 1997 John Wiley & Sons, Inc. J Polym Sci A: Polym Chem 35: 1133–1137, 1997.     

Synthesis of end‐functionalized polymers and copolymers of cyclopentadiene with vinyl ethers by cationic polymerization

A series of cyclopentadiene (CPD)‐based polymers and copolymers were synthesized by a controlled cationic polymerization of CPD. End‐functionalized poly(CPD) was synthesized with the HCl adducts [initiator = CH₃CH(OCH₂CH₂X)Cl; X = Cl ( 2a ), acetate ( 2b ), or methacrylate] of vinyl ethers carrying pendant functional substituents X in conjunction with SnCl₄ (Lewis acid as a catalyst) and n‐Bu₄NCl (as an additive) in dichloromethane at −78 °C. The system led to the controlled cationic polymerizations of CPD to give controlled α‐end‐functionalized poly(CPD)s with almost quantitative attachment of the functional groups (F_n ∼ 1). With the 2a or 2b /SnCl₄/n‐Bu₄NCl initiating systems, diblock copolymers of 2‐chloroethyl vinyl ether (CEVE) and 2‐acetoxyethyl vinyl ether with CPD were also synthesized by the sequential polymerization of CPD and these vinyl ethers. An ABA‐type triblock copolymer of CPD (A) and CEVE (B) was also prepared with a bifunctional initiator. The copolymerization of CPD and CEVE with 2a /SnCl₄/n‐Bu₄NCl afforded random copolymers with controlled molecular weights and narrow molecular weight distributions (weight‐average molecular weight/number‐average molecular weight = 1.3–1.4). © 2000 John Wiley & Sons, Inc. J Polym Sci A: Polym Chem 39: 398–407, 2001     

Synthesis and Characterization of Novel Glycerol‐Derived Polycarbonates with Pendant Hydroxyl Groups

Summary: A novel type of glycerol‐derived, water‐soluble polycarbonate with pendant, primary hydroxyl groups was prepared from 2‐(2‐benzyloxyethoxy)trimethylene carbonate (BETC). Ring‐opening polymerization of BETC and 2,2‐dimethyltrimethylene carbonate (DTC) gave narrow distribution of homopolymers or random copolymers with high molecular weights. The protecting benzyl groups were removed by catalyzed hydrogenation at atmosphere H₂ pressure to give hydroxyl polycarbonates without observable changes on the polymer backbone and molecular weight distribution. The hydrophilicity of the copolymers increases with the increase in the hydrophilic glycerol‐derived carbonate content.

Synthesis of the glycerol‐derived polycarbonate.     

Unusual cationic copolymerization behavior of a six‐membered ring spiro‐orthocarbonate bearing adamantane backbones with a monofunctional epoxide

Copolymerizations of a six‐membered ring spiro‐orthocarbonate bearing adamantane backbones ( AD ‐ SOC , 1 ) and a monofunctional epoxide, PGE , in the presence of cationic initiators such as Sc(OTf)₃ were carried out under various reaction conditions. As a result, instead of the anticipated poly(ether‐ether‐carbonate) 11 , two types of copolyethers ( 12 and 18 ) consisting of two or three types of ether components having different substituent groups were unusually formed along with the evolution of carbon dioxide gas, in which AD ‐ SOC efficiently acted as the corresponding oxetane equivalent monomers 3 and 4 . Furthermore, the copolymerization behavior, including the formation of copolyethers 12 and 18 , unexpectedly and significantly depended on the reaction conditions, such as the concentration of the initiator. For example, the copolymerizations with 5 mol % of Sc(OTf)₃ mainly afforded copolyether 18 , while those with 1 mol % mainly gave copolyether 12 . In addition, treatments with 5 mol % of Sc(OTf)₃ also yielded CH₂Cl₂, THF, and DMF‐insoluble networked products, indicating relatively higher thermal stability compared with a common polyether. © 2005 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 43: 1729–1740, 2005