Ring-opening Polymerization Of L-lactide Research Articles

Self-assembled filomicelles prepared from polylactide-poly(ethylene glycol) diblock copolymers for sustained delivery of cycloprotoberberine derivatives

Polylactide-poly(ethylene glycol) (PLA-PEG) block copolymers were synthesized by ring opening polymerization of l-lactide using a monomethoxy PEG (mPEG) as macroinitiator and zinc lactate as catalyst. The resulting diblock copolymers were characterized by 1H NMR and GPC. Polymeric micelles were prepared by self-assembly of copolymers in distilled water using co-solvent evaporation or membrane hydration methods. The resulting micelles are worm-like in shape as shown by TEM measurements. A hydrophobic anticancer drug, cycloprotoberberine derivative A35, was successfully loaded in PLA-PEG filomicelles with high encapsulation efficiency (above 88%). Berberine (BBR) was studied for comparison. In both methods, PLA-PEG filomicelles were prepared with a theoretical loading of 5%, 10% and 20%. Physical stability studies indicated that BBR/A35-loaded filomicelles were more stable when stored at 4 °C than at 25 °C. Compared with BBR-loaded filomicelles, A35-loaded filomicelles exhibited higher antitumor activity. Importantly, the in vitro cytotoxicity and stability of A35-loaded filomicelles evidenced the potential of drug-loaded filomicelles in the development of drug delivery systems.

Fully biobased thermoplastic elastomers: Synthesis of highly branched linear comb poly(β-myrcene)-graft-poly(l-lactide) copolymers with tunable mechanical properties

Biobased thermoplastic elastomers are of interest for their merits, especially renewability and sustainability. In this work, a series of fully biobased linear comb poly(β-myrcene)-graft-poly(l-lactide) (PM-g-PLLA) copolymers consisting of interior rubbery block and exterior semicrystalline block were synthesized via ring-opening polymerization of l-lactide using hydroxylated poly(β-myrcene) as macroinitiator. To evaluate the effects of branch length and graft density of poly(β-myrcene) on the performances of these obtained copolymers, the chemical compositions and molecular weights, crystal structures and spherulite morphologies, phase morphologies, thermal and mechanical properties were systematically analyzed by various techniques. Analysis of NMR and GPC indicated that graft copolymers were successfully obtained as designed. Two distinct glass transitions corresponding to the two building blocks observed from both DMA and DSC measurements suggested the occurrence of microphase separation, which was further confirmed by SAXS and AFM morphological characterizations. Results of DSC, WAXD, and POM showed that the crystallization behavior of the graft copolymers depends on graft density and branch length. Tensile test suggested that the mechanical properties of graft copolymers depend on PM/PLLA composition, particularly graft density and branch length, which could be readily tailorable to different applications.

Factors influencing catalytic behavior of titanium complexes bearing bisphenolate ligands toward ring-opening polymerization of L-lactide and ε-caprolactone

Factors influencing catalytic behavior of titanium complexes bearing bisphenolate ligands toward ring-opening polymerization of L-lactide and ε-caprolactone

Self-catalyzed surface grafting of Mn3O4 nanoparticles with polylactide and its magnetic properties

Magnetic properties of nanoparticles are size dependent and surface grafting of nanoparticles not only prevents their agglomeration but can also lead to effective domains separation. Present study deals with the synthesis of manganese oxide nanoparticles (< 5 nm) by microwave assisted solvothermal process and its grafting with poly L-lactic acid by a self-catalyzed ring opening polymerization of L-lactide. The Mn3O4 nanoparticles and Mn3O4/PLLA nanocomposite were characterized by many analytical techniques such as FT-IR, TEM, 1H NMR, 13C NMR, XRD, XPS, TGA and DSC etc. The magnetic properties of nanoparticles and nanocomposites were studied using VSM and SQUID showed marked shift in magnetic behavior of Mn3O4 nanoparticles which were super paramagnetic, on coating with PLLA.

Design of bio-based conductive and fast crystallizing nanocomposites with controllable distribution of multiwalled carbon nanotubes via interfacial stereocomplexation

In this study, a novel route was proposed to fabricate entirely bio-based conductive nanocomposites with a low percolation threshold of conductivity (ϕc) and enhanced crystallization and mechanical performances. In order to achieve this objective, poly(d-lactide)/poly(hydroxyalkanoate) (PDLA/PHA) nanocomposites with multiwalled carbon nanotubes (MWCNTs) and MWCNTs-g-PLLA (prepared via ring opening polymerization of l-lactide with grafting degree of 17%) were designed and fabricated. The grafting of PLLA facilitates the selective distribution of MWCNTs in the sole PDLA phase via interfacial stereocomplexation, which in combination with the volume exclusion effect of PHA leads to a lower value of ϕc (ϕc = 0.32 wt%) compared to that of the unmodified MWCNTs (ϕc = 0.56 wt%). The localization of MWCNTs-g-PLLA in the PDLA phase was directly confirmed by scanning electron microscopy, transmission electron microscopy and supported by crystallization analysis by differential scanning calorimetry, X-ray diffraction, and polarizing optical microscopy. The presence of MWCNTs, in particular, the MWCNTs-g-PLLA significantly enhanced the crystallization rate of PDLA. Furthermore, MWCNTs networks in the nanocomposites were monitored by rheological analysis when the MWCNTs and MWCNTs-g-PLLA loading reached a critical value. The MWCNTs networks not only resulted in conductivity, but also strong reinforcement of the nanocomposites. For example, tensile strength of the PDLA/PHA blends increased from 32 to 50 MPa after the formation of MWCNTs network and leveled off at higher MWCNTs loadings. The bio-based conductive nanocomposites reported in this study exhibit significant potential in antistatic films and (semi-)conducting materials.

Micelles of polylactide–poly(ethylene glycol)–polylactide (LA n –EG m –LA n ) triblock copolymers as insulin delivery system: spectroscopic studies

A series of triblock copolymers are synthesized by the ring-opening polymerization of l-lactide in the presence of PEG of various molecular weights. Firstly, the (lactic acid) n –(ethylene glycol) m –(lactic acid) n (LA n –EG m –LA n ) copolymers are characterized by 1H NMR and GPC studies. Micelles, prepared in aqueous media by the direct dissolution method, are characterized by TEM and DLS. In vitro release behavior of bovine insulin from LA37–EG136–LA37 micelles is evaluated at 37 °C. According to results, nearly 90 wt% of insulin is released over 6 days by diffusion in a biphasic pattern. Secondly, a comparative study of the interactions occurring between insulin (both bovine and human) and the LA37–EG136–LA37 triblock copolymer is carried out using different spectroscopic techniques. UV–visible spectroscopy shows that the copolymer binds spontaneously to both proteins with a similar stoichiometry. However, a higher affinity was observed for bovine insulin. Far-UV CD spectroscopy reveals that the secondary structure of both proteins changes in the presence of the copolymer, although the extent of changes in bovine insulin is larger. Acrylamide quenching experiments display reduced accessibility of tyrosines at high copolymer concentrations. In these conditions, the major decrease in the α-helical content of the proteins causes tyrosines to be exposed to the nonpolar environment of the micelles and thus shielded from the aqueous solvent. Results demonstrate that upon interaction with the copolymer, the microenvironment around tyrosines is rearranged, the extent of which depends on the copolymer concentration. Altogether, drug–copolymer interactions need to be considered when attempting to use polymeric formulations as delivery carriers of peptide drugs.

Synthesis and characterization of bovine serum albumin-loaded microspheres based on star-shaped PLLA with a xylitol core and their drug release behaviors

The star-shaped poly(l-lactide) (s-PLLA) was synthesized via ring-opening polymerization of l-lactide, with xylitol as a multifunctional initiator and stannous octoate as a catalyst. The structures of s-PLLA were characterized by 1H NMR spectroscopy, while the molecular weight (M w) and polydispersity index were determined by gel permeation chromatography. Bovine serum albumin (BSA) loaded s-PLLA microspheres were fabricated by a water–oil–water (W 1/O/W 2) double-emulsion solvent evaporation method. The morphology, drug encapsulation efficiency (EE), and in vitro release behavior of the prepared microspheres were studied in detail. Results indicated that the average diameters of s-PLLA microspheres could be controlled between 7 and 15 µm by varying the s-PLLA’s concentration or M w, and the drug encapsulation efficiency of BSA-loaded microspheres were 10–42%. The in vitro study shows that the BSA-loaded microspheres prepared by high molecular weight s-PLLA had a slow cumulative release behavior in phosphate buffer saline (PBS, pH 7.4) and the release process followed the Baker–Lonsdale equation. Present work supposes that the synthesized s-PLLA is a good candidate for drug delivery.

Multiblock Thermoplastic Elastomers Derived from Biodiesel, Poly(propylene glycol), and l-Lactide

A series of [poly(l-lactide)–poly(dimer acid methyl ester-alt-poly(propylene glycol))–poly(l-lactide)]n (PLLA–PDP–PLLA)n multiblock copolymers was synthesized in a three-step procedure: PLLA–PDP–PLLA (LDPL) triblock copolymers were synthesized using ring-opening polymerization of l-lactide with PDP macroinitiators, which was prepared via step-growth melt polycondensation based on biodiesel and macro-diol, followed by chain extension of the LDPL triblock with 4,4′-methylenebis(phenyl isocyanate). Molecular characterization revealed that the synthetic procedures yielded the desired triblock and multiblock copolymers (fPLLA = 0.22–0.27). The relationship between thermal behavior and morphology indicated microphase separation into two domains in both the triblocks and multiblocks. Compared to previously reported triblocks with a high molar mass and PLLA hard blocks with inaccessible order–disorder transition temperature (TODT) values, the multiblock architectures in this study were found to become disordered at much lower temperatures (TODT = 82–128 °C). To prepare (LDPL)n multiblocks, coupling low-molar-mass LDPL triblocks without free-standing thin films led to dramatically enhanced tensile properties. The self-adhesive performance of the pressure-sensitive adhesive (PSA) system including the multiblocks was evaluated, showing a peel strength of 3.1 N cm–1, a probe tack of 1.9 N, and static shear strength of >50 000 min, which are values comparable to those of current PSAs. These biodiesel-based thermoplastic elastomers hold promise for sustainability and high value-added economy.

Novel Poly(l-lactide)/graphene oxide films with improved mechanical flexibility and antibacterial activity

Poly(l-lactic acid) (PLLA) is a biocompatible polyester derived from renewable sources. It is desirable to reduce its brittleness and introduce antibacterial activity for biomedical applications by using graphene oxide (GO) as a structural and antibacterial agent. However, commonly used polymer/GO composite synthesis methods, such as physical mixing and covalent functionalization, either cause phase segregation or compromise the intrinsic properties of GO. Here, a novel approach is demonstrated to synthesize PLLA/GO films. First, perylene bisimides-containing PLLA (PBI-PLLA) was synthesized via ring-opening polymerization of l-lactide using a hydroxyl-derivate of perylene bisimides (PBI-OH) as the initiator. Next, PBI-PLLA was conjugated with GO via π-π stacking to form PLLA-conjugated GO (PLLA-c-GO). Last, PLLA/GO films were fabricated by simple solution casting of commercial PLLA and PLLA-c-GO dissolved in chloroform. Detailed characterization shows that GO retains its morphology and functional groups in PLLA-c-GO, which enables unique properties in the PLLA/GO films. The starting thermal degradation temperature of PLLA/GO films in N2 increases to 313°C comparing to commercial PLLA films at 293°C. Their surface is more hydrophilic with the water contact angle of 53°. Their elongation at break improves significantly from 3% to 30% compared to commercial PLLA films, demonstrating much better flexibility. Most importantly, the PLLA/GO films show good antibacterial activity towards Escherichia coli (E. coli), Staphylococcus aureus (S. aureus), and Bacillus subtiliscells (B. subtilis) cells with the bacterial colony number reduction by 80%. At the same time, they show low toxicity towards mammalian cells, such asL929 and macrophage cells. Overall, the novel PLLA/GO films demonstrate various beneficial characteristics for potential biomedical applications.

Piperidine-conjugated polyfunctional star-shaped PLLA as a novel bio-based antioxidant additive for bioplastics

Antioxidant-conjugated star-shaped PLLA (star-PLLA-PPD) were originally proposed as a novel polyfunctional free radical stabilizing additive for bioplastics. By a simple ring opening polymerization of l-lactide (L-LA) on a poly-functional core molecule (i.e., pentaerylthritol) using tin (II)-2-ethylhexanoate (SnOct2) as a catalyst, the 4-arms star-shaped PLLA was successfully prepared and confirmed by FT-IR and 1H-NMR. Percent conversion of L-LA to 4-arms star-PLLA was 78.50% and the weight and number average molecular weights determined by GPC were 34726 Da and 27286 Da, respectively (PDI = 1.27). Piperidine (PPD) was then conjugated onto 4-arms star-PLLA to obtain star-PLLA-PPD. As observed by SEM and DSC, the star-PLLA-PPD exhibited excellent compatibilizer as well as nucleating agent for PLA. A model study on free radical scavenging ability of the star-PLLA-PPD in PLA blends was carried out under radiation-induced free radical process. Irradiation doses of 10 kGy and 25 kGy were used because they are generally used for food and medical device sterilization, respectively. Free radical scavenging ability was demonstrated using EPR spectroscopy. The star-PLLA-PPD efficiently scavenges the free radicals in PLA matrix upon irradiation. The star-PLLA-PPD additive could retard the degradation of PLA under irradiation as observed by protecting molecular weight reduction when compared with the neat PLA. The migration of star-PLLA-PPD is significant lower than PPD. A novel star-PLLA-PPD additive would be a good model of polyfunctional bio-based antioxidant additive for bioplastics especially for food packaging and biomedical materials.

Exploration of tertiary aminosquaramide bifunctional organocatalyst in controlled/living ring-opening polymerization of l-lactide

A series of tertiary aminosquaramides as bifunctional organocatalysts in the ring-opening polymerization (ROP) of l-lactide (l-LA) were developed, allowing the activation of both the l-LA monomer and the alcohol group of the initiator/propagating species. Further, the impact of tertiary nitrogen substituents on catalytic activity in ROP of l-LA was explored. The tertiary aminosquaramide— an air-stable and moisture-stable catalyst—exhibited superior activity in contest with thiourea counterpart when both were equipped with a similar tertiary amine group. Kinetic and chain-extension experiments indicated that the formed poly(l-LA) is featured with narrow polydispersity and high end-group fidelity, hallmarks of a living polymerization process. The initiator efficiency was further executed at ease by preparation of an ABA triblock copolymer poly (l-LA)-b-poly (ethylene glycol)-b-poly (l-LA) in the presence of a dual-headed PEG macroinitiator. 1H NMR titration experiments suggested a bifunctional catalytic mechanism, wherein both the l-LA monomer and the propagating hydroxyl group were activated en route to polymerization. The 1H NMR, SEC, and MALDI-TOF MS measurements validated the quantitative incorporation of the initiator in the polymeric chains and enchainment over competitive trans-esterification reaction. Overall, the structure-activity relationships were surveyed to uncover aminosquaramide as a new bifunctional dual hydrogen-bond donor catalyst for living ROP of l-LA. © 2017 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2017

Synthesis of poly(l-lactide) by static mixing reaction technique via ring-opening polymerization of l-lactide

A green, rapid and energy-saving synthesis method of poly(l-lactide) (PLLA) via ring-opening polymerization (ROP) of l-lactide was developed in this work. The ROPs were performed in a tubular static mixing reactor. The effects of properties of l-lactide, catalyst dosage, polymerization temperature, flow rate of reactants and reaction time on the properties of resultant polymers were investigated. The results showed that high quality PLLA polymer with a Mw of 166,000, a PDI of 1.48 and an optical purity over 99% could be obtained in a relatively short reaction time (90min) under suitable reaction conditions by using this technique. Therefore, this method is an low-carbon and high-efficient process for synthesizing high quality PLLA.

In situ foamable, degradable polyurethane as biomaterial for soft tissue repair

Degradable foams which can be inserted endoscopically as liquid or pasty mixtures into soft tissue defects possess a promising potential for the surgical treatment of such defects. The defects can be sealed under in situ foaming and simultaneous material expansion. We developed an in situ foamable (l-lactide-co-ε-caprolactone)-based, star-shaped prepolymer by ring opening polymerization of l-lactide and ε-caprolactone in the presence of meso-erythritol as starter. By conversion of the terminal hydroxyl groups of the formed oligoester with lysine diisocyanate ethyl ester (LDI) an isocyanate-endcapped, reactive prepolymer has been received. Foaming can be initiated by addition of 1,4-diazabicyclo[2,2,2]octane (DABCO), water, LDI and DMSO. By varying the composition of these additives, the foaming and curing time could be varied within a clinically acceptable range. A porosity of approximately 90%, and an average tensile strength of 0.3MPa with elongations of 90% were determined for the foams.In vitro cytotoxicity on cured foams was assayed on 3T3 fibroblasts and demonstrated an excellent cytocompatibility. This was also confirmed in an in vivo study using an established rat model, where prefabricated foams and in situ hardening material were inserted into subdermal skin incisions in parallel. The feature of chronic inflammation was only weakly developed in both groups and slightly more pronounced and persisted for longer time in the group of in situ foamed material. In both groups the foreign materials were vascularized, degraded and substituted by connective tissue. The results encourage to proceed with trials where the materials are used to fill more heavily loaded defects.

Optimization of controlled ring-opening polymerization of l-lactide to hydroxyl terminated polylactides using zinc acetate catalyst

Hydroxyl terminated polylactide polymers with number of average molecular weights (M n ) varying from 1625 to 3459 g mol−1 were synthesized by ring opening bulk polymerization of lactide in the presence of zinc acetate being a potent catalyst. The use of 1,4 butanediol (BDO) initiator leads to hydroxyl terminated polylactides, thus excellent precursors for shape-memory biodegradable polyurethanes. Different reaction conditions employed for the synthesis of hydroxyl terminated polylactide polymers via activated monomer mechanism may result in differences in M n , percentage mass conversion and percentage degree of crystallinity (%χ c ) of the product. Influence of process parameters, i.e. catalyst concentration, initiator concentration, reaction temperature and time on characteristics of hydroxyl terminated polylactides was studied. These polymers were characterized by Nuclear Magnetic Resonance (1H-NMR) spectroscopy, Fourier transforms infrared (FTIR) spectroscopy, gel permeation chromatography (GPC) and X-ray diffraction (XRD) techniques. FTIR and 1H-NMR confirmed the formation of hydroxyl terminated polylactides. M n was determined by 1H-NMR, GPC and end group analysis. %χ c was calculated from XRD spectra. Maximum mass conversion, M n and %χ c were observed at 5 mol% SnOct2 and 5 mol% BDO concentration. At optimum temperature of 145 °C, these characteristics improved linearly with polymerization time up to 6 h and declined thereafter.

Investigation of redox switchable titanium and zirconium catalysts for the ring opening polymerization of cyclic esters and epoxides

The synthesis and characterization of (thiolfan*)Zr(OtBu)2 (thiolfan* = 1,1′-di(2,4-di-tert-butyl-6-thiophenoxide)ferrocene) is reported, as well as its activity toward the ring-opening polymerizations of l-lactide and ε-caprolactone.

L-lactide ring-opening polymerization on a magnesium catalyst based on acenaphthene-1,2-diimine ligand: Development of biocompatible materials for osteoplasty

Isotactic poly-L-lactide was prepared by L-lactide ring-opening polymerization in tetrahydrofuran solution in the presence of a magnesium complex derived from 1,2-bis-[(2,6-diisopropyl)phenylimino]acenaphthene (dpp-bian). Polymer specimens in the form of cylindrical blocks, prepared by hot molding, were tested in experiments with human dermal fibroblast cultures. The polymers prepared exhibit no cytotoxicity, which opens prospects for performing their preclinical animal tests.

Effect of surface modification of cellulose nanocrystal on nonisothermal crystallization of poly(β-hydroxybutyrate) composites

Ring-opening polymerization of l-lactide from cellulose nanocrystal (CNC) surface yielded polylactide-grafted CNC (CNC-g-PLA). The structure and chemical composition of the CNC-g-PLA were characterized by FT-IR, 1H NMR, XPS and XRD. The crystallization behavior and lamellar structure of poly(β-hydroxybutyrate) (PHB) in the presence of pristine CNC and CNC-g-PLA were elucidated via DSC and SAXS, and Babinet's reciprocity theory was applied. Crystallization kinetics were further analyzed using Ozawa, Mo and Kissinger models. In the presence of pristine CNC, nucleation of PHB crystals led to an increase in the crystallization temperature (Tc) of PHB; while CNC-g-PLA acted as antinucleation agent, resulting in a remarkable reduction in Tc of PHB. Accordingly, the composite with pristine CNC possessed a higher crystallization rate than neat PHB, while CNC-g-PLA displayed the lowest crystallization rate. However, the lamellar structure of PHB was not affected by the presence of pristine and modified CNCs, and almost identical crystallization activation energies as the neat PHB were observed, indicating that nucleation is dominant during PHB crystallization, instead of crystal growth. This study offers a promising approach of using pristine and modified CNCs to control the crystallization of biodegradable aliphatic polyesters.

Novel tri- and tetrafunctional cholic acid-based initiators for the synthesis of star-shaped poly(L-lactide)s

In this investigation, two novel multifunctional initiators for ring-opening polymerization were synthesized in three steps starting from cholic acid. Thus, cholic acid (1a) and its methyl ester (1b) were quantitatively transformed, via solvent-free reaction with succinic anhydride, to the corresponding 3, 7, 12-tri-hemisuccinate derivatives (3a-b). The polyacidic compounds (3a-b) were treated with thionyl chloride affording the corresponding acyl chlorides 4a-b which, in turn, were reacted with ethylene glycol to give the derivatives 2a-b having three and four primary alcohol end groups. These compounds, fully characterized by 1H, 13C NMR and mass spectrometry, have been assessed as initiators in the ring-opening polymerization of L-lactide using stannous octanoate as catalyst. The resulting three- and four-armed star-shaped poly(L-lactide)s, which were characterized by 1H NMR, SEC, DSC and TGA analysis, were amorphous, and their glass transition temperatures ranged from 13.7 to 36.5 °C. Additionally, some cholic acid-based star-shaped polylactic structures recently published have been critically reconsidered showing that these molecules, described as star polymers, were actually linear polymers.

Reinforced Mechanical Properties and Tunable Biodegradability in Nanoporous Cellulose Gels: Poly(L-lactide-co-caprolactone) Nanocomposites.

Incorporation of nanofillers into aliphatic polyesters is a convenient approach to create new nanomaterials with significantly reinforced mechanical properties compared to the neat polymers or conventional composites. Nanoporous cellulose gels (NCG) prepared from aqueous alkali hydroxide/urea solutions can act as alternative reinforcement nanomaterials for polymers with improved mechanical properties. We report a simple and versatile process for the fabrication of NCG/poly(L-lactide-co-caprolactone) (NCG/P(LLA-co-CL) nanocomposites through in situ ring-opening polymerization of L-lactide (LLA) and ε-caprolactone (ε-CL) monomers in the NCG. The volume fraction of the NCG in the nanocomposites was tunable and ranged from 4.5% to 37%. Fourier transform infrared (FT-IR), X-ray diffraction (XRD), and differential scanning calorimetry (DSC) results indicated that P(LLA-co-CL) were synthesized within the NCG and partially grafted onto the surface of the cellulose nanofibrils. The glass-transition temperature (Tg) of the NCG/P(LLA-co-CL) nanocomposites could be altered by varying the molar ratio of LLA/ε-CL and was affected by the volume fraction of NCG. Atomic force microscopy (AFM) and scanning electron microscopy (SEM) images confirmed that the interconnected nanofibrillar cellulose network structure of the NCG was finely distributed and preserved in the P(LLA-co-CL) matrix after polymerization. The dynamic mechanical analysis (DMA) results showed remarkable reinforcement of the tensile storage modulus (E') of the P(LLA-co-CL) nanocomposites in the presence of NCG, especially above the Tg of the P(LLA-co-CL). The modified percolation model agreed well with the mechanical properties of the NCG/P(LLA-co-CL) nanocomposites. The introduction of NCG into the P(LLA-co-CL) matrix improved the mechanical properties and thermal stability of the NCG/P(LLA-co-CL) nanocomposites. Moreover, the NCG/P(LLA-co-CL) nanocomposites have tunable biodegradability and biocompatibility and potential applications in tissue engineering repair, biomedical implants, and packing.

Titanium complexes based on pyridine containing dialcohols: Effect of a ligand

Substituted 2,6-bis(hydroxyalkyl)pyridines, H2L, 1–3 (2,6-Py(CH2(X)OH)(CH2(Y)OH), X=Y=cyclo-C6H10, 1; X=Y=1-Ad, 2; X=CPh2, Y=CH2CPh2, 3), were used as ligands for the synthesis of titanium(IV) complexes, (i-PrO)2Ti(L), 1a–3a. On the contrary, application of related dialcohol based on 2,2′-bipyridine, H2L′, 5 (2,2′-bipy-6,6′-(CH2Ph2OH)2), resulted in titanyl complex, (L′)TiO, 6. The molecular structure of 6 was investigated by X-ray analysis. Compounds 1a and 3a were tested as initiators in ring-opening polymerization of l-lactide and ε-caprolactone showing moderate activity.