Ring‑opening polymerization of β‑butyrolactone in the presence of alkali metal salts: investigation of initiation course and determination of polymers structure by MALDI‑TOF mass spectrometry

Several alkali metal salts that activated 18-crown-6 were applied as initiators of β-butyrolactone anionic ring-opening polymerization in tetrahydrofuran at room temperature. Some of them, i.e., Ph2PK, Ph3HBK, ( Me3Si)2NK, and t-BuOK, deprotonate the monomer which results in macromolecules with trans-crotonate starting group. Other salts, for example, MeOK, i-PrOK, PhCH2OK, and CbK (Cb denotes carbazolyl group), deprotonate monomer or open its ring in the acyl-oxygen position. After ring-opening KOH forms as intermediate and initiates further polymerization. Ph3CK and monopotassium salt of ethylenediaminetetraacetic acid also deprotonate monomer and open its ring, however, in the alkyl-oxygen position. Monopotassium salts of glycolic acid, diglycolic acid, or malonic acid initiate polymerization mainly by ring opening in the alkyl-oxygen position. It results in the formation of polymers with two reactive terminal groups. The salts used react with the monomer as strong bases, nucleophilic bases, or nucleophiles. It determines unsaturation of the polymers obtained in the wide range of 2–100 mol%

Mechanism of ε‑caprolactone polymerization in the presence of alkali metal salts: investigation of initiation course and determination of polymers structure by MALDI‑TOF mass spectrometry

Various alkali metal salts were applied as initiators for ε-caprolactone anionic ringopening polymerization in tetrahydrofuran at room temperature. It was observed that potassium methoxide (MeOK), potassium isopropoxide (i-PrOK) and potassium tert-butoxide (t-BuOK) nonactivated or activated by 18-crown-6 (18C6) initiated polymerization mainly by deprotonation of the monomer. In the case of potassium hydride (KH), its basicity increased with the ability of the ligand for cation complexation. For example, KH without ligand or with weak ligands for K+ as 12C4 reacted exclusively by ring opening. However, in the presence of strong ligands, as 15C5, 18C6 or cryptand C222, basicity of H− increased with the ability of the ligand for cation complexation. In the last case, ~ 32% of the monomer was deprotonated. In these systems, gaseous H2 evolved during the initiation. Deprotonation of the monomer by some initiators resulted in macromolecules with reactive aldehyde group or lactone ring as starting groups. They took part in the reaction with potassium alkoxide active centers of growing chains leading to the formation of branched poly(ε-caprolactone)s. Sodium hydride (NaH) was inactive, but in the presence of 15-crown-5 or 18-crown-6 initiated polymerization exclusively by ring opening. MALDI-TOF mass spectrometry supported with 13C NMR and SEC was used for analysis of the polymers obtained. Mechanism of the studied processes was proposed and discussed

Characterization of new polyether-diols with different molar masses and modality prepared by ring opening polymerization of oxiranes initiated with anhydrous potassium hydroxide

Several new polyether-diols were prepared by ring-opening polymerization of monosubstituted oxiranes in the presence of anhydrous potassium hydroxide. 1,2-Butylene oxide (BO), styrene oxide (SO), isopropyl glycidyl ether (IPGE), allyl glycidyl ether (AGE), phenyl glycidyl ether (BGE), p-methoxyphenyl glycidyl ether (MPGE) and benzyl glycidyl ether (BGE) were chosen as monomers. Macrocyclic ligands complexing metal cations, i.e. coronand 18C6 or cryptand C222 were used as activators in these systems. All polymerizations were carried out in tetrahydrofuran solution at room temperature. Molar mass (Mn) and dispersity (Mw/Mn) of the polymers obtained with KOH depends on the kind of monomer, initial concentration of the initiator and the presence and kind of ligand or water. For example, PBO-diols prepared without ligand are bimodal and for the main fraction Mn>Mcalc. However, after addition of 18C6 polymers are unimodal and unexpectedly have much higher Mn = 13,700–15,800 and very low dispersity (Mw/Mn = 1.04–1.08). Mn of PBO-diols decrease with increase of [KOH]o and do not change at [BO]o = 2.0–9.0 mol/dm3. Addition of C222 results inMn decrease of PBO-diols. Similar effects were observed in the polymerization of PAGE-diols and PPGE-diols. In the polymerization of SO, PGE, MPGE and BGE initiator efficiency ( f ) is high and Mn<Mcalc. Polymodality of some polymers obtained was discussed in term of the formation of various species propagating with different rate constants

Anionic ring-opening copolymerization of styrene oxide with monosubstituted oxiranes: analysis of composition of prepared new copolyether-diols by MALDI-TOF mass spectrometry

Several new random copolyethers of styrene oxide (SO) and other monosubstituted oxirane as comonomer, i.e., propylene oxide (PO), isopropyl glycidyl ether (IPGE) or allyl glycidyl ether (AGE), were synthesized in THF solution at room temperature. As initiator monopotassium salt of dipropylene glycol activated by 18-crown-6 complexing agent was used. Synthesized copolyether-diols were characterized by SEC, 13C NMR and MALDI-TOF techniques. They were unimodal and had Mn = 3500–4600 and relatively low dispersity (Mw/Mn = 1.16–1.18). Low unsaturation of the products resulted from chain transfer reaction to styrene oxide. Composition of SO/PO-diol, SO/IPGE-diol and SO/AGE-diol copolymers was determined by MALDI-TOF mass spectrometry. Homopolymers were not formed during the processes

The influence of initiator and macrocyclic ligand on unsaturation and molar mass of poly(propylene oxide)s prepared with various anionic system

Anionic polymerization of propylene oxide was carried out in the presence of two groups of potassium salts activated 18-crown-6 (18C6), e.g. alkoxide salts (CH3OK, i-PrOK, t-BuOK, CH3OCH2CH(CH3)OK, KCH2O) and other salts (CbK, Ph3CK, Ph2PK, Ph3HBK, KK, KH, and [(CH3)3Si]2NK) in THF at room temperature. Application of various initiating systems results in polyethers which are different in level and kind of unsaturation represented by allyloxy, cis- and trans-propenyloxy, as well as vinyloxy starting groups. In the presence of selected initiator, i.e. t-BuO-K? unsaturation increases markedly by addition of 18C6 or C222. During the initiation step oxirane ring-opening and direct deprotonation of the monomer occur simultaneously involving in some cases also the ligand. All initiators opens oxirane ring in the b-position except i-PrOK, which opens it in the b- and a-position. The mechanisms of the reactions were discussed

Application of cesium hydroxide monohydrate for ring opening polymerization of monosubstituted oxiranes : characterization of synthesized polyether-diols

Cesium hydroxide monohydrate (CsOH·H2O) activated by cation complexing agents, i.e., 18C6 or C222 was applied as initiator of monosubstituted oxiranes polymerization. Propylene oxide (PO), 1,2-butylene oxide (BO), styrene oxide (SO) and some glycidyl ethers were used as monomers. All processes were carried out in tetrahydrofuran solution at room temperature. Such polymers, as PPO-diols, PBO-diols and PSO-diols, are unimodal and have molar masses Mn = 2000-5100. Their dispersities are rather high (Mw/Mn = 1.17-1.33). Moreover, PPO-diols and PSO-diols are not contaminated by monools with unsaturated starting groups. Poly(glycidyl ether)s are, in general, polymodal. For example, poly(isopropyl glycidyl ether)-diols are bi- or trimodal, whereas poly(allyl glycidyl ether)-diols possess two or even six fractions. Molar masses of main fraction are 4200-6400, and the second fraction is much lower, namely 600-2600. Dispersities of some fractions are very low (Mw/Mn = 1.01-1.07). Polymodality of polymers obtained was discussed in terms of the formation of two or more species propagating with different rate constants

New way of anionic ring-opening copolymerization of β-butyrolactone and ε-caprolactone : determination of the reaction course

Poly(ε-caprolactone)-block-poly(β-butyrolactone) copolymers were prepared in two-step synthesis. Firstly, poly(ε-caprolactone) (PCL) was obtained by anionic ring-opening polymerization of CL initiated with anhydrous KOH activated 12-crown-4 cation complexing agent. Reaction was carried out in tetrahydrofuran solution and argon atmosphere at room temperature. Then, β-butyrolactone (BL) and 18-crown-6 were added to the system, resulting in PCL-block-PBL copolymer, which contains after methylation hydroxyl starting group and methyl ester end group. The main product was contaminated with PCL and PBL homopolymers formed in a side reactions. 13C NMR technique was used for determination of chemical structure of polymers obtained. The course of the studied processes was proposed. MALDI-TOF technique was used to reveal the macromolecules’ architecture where several series were found. The identified series shown that mainly copolymeric macromolecules were formed with scare contribution of homopolymeric polybutyrolactone with trans-crotonate starting groups and polycaprolactone, which is congruent with the proposed reaction mechanism. Moreover, critical approach concerning previously reported PCL-block-PBL copolymer synthesis by use of NaH as initiator was also presented

Novel concept of polymers preparation with high photoluminescent quantum yield

A series carbazolyl-containing polymers were synthesized by anionic polymerization of various oxiranes and methyl methacrylate. The polymerization was carried out using as initiator carbazylpotassium activated 18-crown-6 in THF. The polymers were prepared and found using size exclusion chromatography to have a degree of polymerization (DPn) about 20 relatively and low dispersity in the range of 1.07–1.66. Their optical properties were investigated by means of UV–vis and photoluminescence spectroscopies. The obtained polymers emitted light with maximum emission about 370 nm and high quantum yield ranging up to 79 %. Thus, it was confirmed that the utilization of fluorophore initiator for polymerization of non photoresponsive monomers is quite efficient for the preparation of photoluminescent polymers

Ring-opening polymerization of monosubstituted oxiranes in the presence of potassium hydride : determination of initiation course and structure of macromolecules by MALDI-TOF mass spectrometry

Several monosubstituted oxiranes were polymerized with suspension of potassium hydride (KH) in tetrahydrofuran (THF) at room temperature. This heterogeneous process resulted in polyethers with various starting groups depending on the kind of monomer. The macromolecules formed in ring-opening polymerization of monosubstituted oxiranes were analyzed by Matrix Assisted Laser Desorption/Ionization - Time of Flight Mass Spectrometry (MALDI-TOF MS). It was stated, that initiation of propylene oxide (PO) polymerization with KH proceeded via three ways, i.e. cleavage of oxirane ring in the β-position, monomer deprotonation and deoxygenation. Potassium isopropoxide, potassium allyloxide and potassium hydroxide were the real initiators. The main reactions, which occur in the initiation step, depend on the type of monomer used. In the case of allyl glycidyl ether (AGE) and phenyl glycidyl ether (PGE) deprotonation of the monomer did not occur. During initiation of glycidyl ethers oxirane ring was opened and also linear ether bond between glycidyl group and oxygen atom was cleaved under influence of KH. Interestingly, formation of new kinds of macromolecules was observed in the systems containing glycidyl ethers, which do not possess mers of the monomers used. Mechanisms of the studied processes were presented and discussed. Carbon-13 Nuclear Magnetic Resonance (13C NMR) was used as supporting technique for analysis of the obtained polymers. Number average molar masses of the polymers (Mn) determined by Size Exclusion Chromatography (SEC) were about two times higher than calculated ones. It indicated that half of used KH did not take part in the initiation step

Application of monopotassium dipropylene glycoxide for homopolymerization and copolymerization of monosubstituted oxiranes : characterization of synthesized macrodiols by MALDI-TOF mass spectrometry

Monopotassium dipropylene glycoxide, activated by a 18-crown-6 cation complexing agent (K-DPG/L, where DPG (dipropylene glycol) is a mixture of isomers) was used as an e ective initiator of the homopolymerization and copolymerization of several monosubstituted oxiranes, i.e., propylene oxide (PO), 1.2-butylene oxide (BO), and some glycidyl ethers such as allyl, isopropyl, phenyl, and benzyl ones (AGE, IPGE, PGE, and BGE, respectively). The copolymers are novel and can be prospectively used for the fabrication of new thermoplastic or crosslinked polyurethanes. All processes were carried out in homogeneous mild conditions, i.e., tetrahydrofuran solution at room temperature and normal pressure. They resulted in new unimodal macrodiols with Mn =Mcalc in the range of 1500–8300, low dispersityMw/Mn = 1.08–1.18 and a chemical structure well defined by several techniques, i.e., MALDI-TOF, size exclusion chromatography (SEC), 13C NMR, and FTIR. Monopotassium salts of homopolyether-diols, i.e., PPO-diol, PBO-diol, and PAGE-diol, appeared to be useful macroinitiators for the preparation of new triblock copolyether-diols by polymerization of glycidyl ethers. In BO/BGE random copolymerization initiated with K-DPG/L, macromolecules of copolyether-diol were exclusively formed. Macromolecules of copolyether-diol accompanied by homopolyether PPO-diol were identified in the PO/PGE system. However, AGE and PGE reacted by giving random copolyether-diol as well as homopolymer-diols, i.e., PAGE-diol and PPGE-diol. Macromolecules of prepared copolyether-diols contain various numbers of mers deriving from comonomers; the kind of comonomer determines the composition of the product. Several prepared homopolyether-diols and copolyether-diols could be useful for the synthesis of new thermoplastic polyurethanes