Ring-opening Polymerization Method Research Articles

Leveraging a rationally designed veliparib-based anilide eliciting anti-leukemic effects for the design of pH-responsive polymer nanoformulation

Careful recruitment of the components of the HDAC inhibitory template culminated in veliparib-based anilide 8 that elicited remarkable cell growth inhibitory effects against HL-60 cell lines mediated via dual modulation of PARP [(IC50 (PARP1) = 0.02 nM) and IC50 (PARP2) = 1 nM)] and HDACs (IC50 value = 0.05, 0.147 and 0.393 μM (HDAC1, 2 and 3). Compound 8 downregulated the expression levels of signatory biomarkers of PARP and HDAC inhibition. Also, compound 8 arrested the cell cycle at the G0/G1 phase and induced autophagy. Polymer nanoformulation (mPEG-PCl copolymeric micelles loaded with compound 8) was prepared by the nanoprecipitation technique. The mPEG-PCL diblock copolymer was prepared by ring-opening polymerization method using stannous octoate as a catalyst. The morphology of the compound 8@mPEG-PCL was examined using TEM and the substance was determined to be monodispersed, spherical in form, and had an average diameter of 138 nm. The polymer nanoformulation manifested pH-sensitive behaviour as a greater release of compound 8 was observed at 6.2 pH as compared to 7.4 pH mimicking physiological settings. The aforementioned findings indicate that the acidic pH of the tumour microenvironment might stimulate the nanomedicine release which in turn can attenuate the off-target effects precedentially claimed to be associated with HDAC inhibitors.

Curing kinetics and plugging mechanism of high strength curable resin plugging material

Lost circulation, a recurring peril during drilling operations, entails substantial loss of drilling fluid and dire consequences upon its infiltration into the formation. As drilling depth escalates, the formation temperature and pressure intensify, imposing exacting demands on plug materials. In this study, a kind of controllable curing resin with dense cross-network structure was prepared by the method of solution stepwise ring-opening polymerization. The resin plugging material investigated in this study is a continuous phase material that offers effortless injection, robust filling capabilities, exceptional retention, and underground curing or crosslinking with high strength. Its versatility is not constrained by fracture-cavity lose channels, making it suitable for fulfilling the essential needs of various fracture-cavity combinations when plugging fracture-cavity carbonate rocks. Notably, the curing duration can be fine-tuned within the span of 3–7 h, catering to the plugging of drilling fluid losing of diverse fracture dimensions. Experimental scrutiny encompassed the rheological properties and curing behavior of the resin plugging system, unraveling the intricacies of the curing process and establishing a cogent kinetic model. The experimental results show that the urea-formaldehyde resin plugging material has a tight chain or network structure. When the concentration of the urea-formaldehyde resin plugging system solution remains below 30%, the viscosity clocks in at a meager 10 mPa·s. Optimum curing transpires at 60 °C, showcasing impressive resilience to saline conditions. Remarkably, when immersed in a composite saltwater environment containing 50000 mg/L NaCl and 100000 mg/L CaCl2, the urea-formaldehyde resin consolidates into an even more compact network structure, culminating in an outstanding compressive strength of 41.5 MPa. Through resolving the correlation between conversion and the apparent activation energy of the non-isothermal DSC curing reaction parameters, the study attests to the fulfillment of the kinetic equation for the urea-formaldehyde resin plugging system. This discerning analysis illuminates the nuanced shifts in the microscopic reaction mechanism of the urea-formaldehyde resin plugging system. Furthermore, the pressure bearing plugging capacity of the resin plugging system for fractures of different sizes is also studied. It is found that the resin plugging system can effectively resident in parallel and wedge-shaped fractures of different sizes, and form high-strength consolidation under certain temperature conditions. The maximum plugging pressure of resin plugging system for parallel fractures with outlet size 3 mm can reach 9.92 MPa, and the maximum plugging pressure for wedge-shaped fractures with outlet size 5 mm can reach 9.90 MPa. Consequently, the exploration and application of urea-formaldehyde resin plugging material precipitate a paradigm shift, proffering novel concepts and methodologies in resolving the practical quandaries afflicting drilling fluid plugging.

Synthesis and characterization of graft copolymer hydrogel by “grafting from” atom transfer radical polymerization using brominated macro monomeric initiator and investigation of hydrogel properties

AbstractIn this study, poly(ɛ-caprolactone-g-2-hydroxy ethyl methacrylate) [P(CL-g-HEMA)] graft copolymer hydrogels were successfully synthesized through multi-step reactions. For this purpose, firstly, hydroxyl-terminated poly(ɛ-caprolactone) (PCL-OH) was obtained by ring-opening polymerization (ROP) method of ɛ-caprolactone using 3-chlor-1,2-propanediol initiator, which is suitable for ring-opening polymerization method. Then, from the reaction of synthesized PCL-OH and 3-bromopropionyl chloride, a new brominated poly(ɛ-caprolactone) (PCL-Br) was synthesized for use as a functionalized atom transfer radical polymerization (ATRP) initiator. Poly(ɛ-caprolactone-g-2-hydroxy ethyl methacrylate) [P(CL-g-HEMA)] graft copolymer hydrogels were synthesized by “grafting from” atom transfer radical polymerization (ATRP) of 2-hydroxy ethyl methacrylate (HEMA) presence the new synthesized functionalized ATRP initiator (PCL-Br) and hydrogel properties were investigated. The synthesized functionalized initiators and graft copolymer hydrogel were characterized by spectroscopic methods such as 1H-NMR, FT-IR, TGA, DSC and SEM. The observation of two different decomposition temperatures, respectively, from the TGA analysis results may support the formation of the biblock graft copolymer. A glass transition temperature (Tg) of the graft copolymer hydrogel was found by DSC, and this value is between the Tg values of the homopolymers forming the graft copolymer hydrogel. Water swelling values of graft copolymer hydrogels were measured and calculated every 24 h in pure water with pH = 7 at from + 4 to 65 °C. Considering the weight of dry graft copolymer hydrogels, it was seen that water was absorbed at most at + 4 °C. As the temperature increased, the water absorption or swelling of the hydrogel decreased.

Nucleolin-targeted cationic nanoparticle for delivery of survivin shRNA against colorectal cancer in vitro and in vivo

In this study, synthesis of Polylactic acid (PLA) polymer was carried out through ring-opening polymerization (ROP) method. Then, 4-cyano-4-(phenylcarbonothioylthio)pentanoic acid as the CTA molecule was attached to the PLA, and subsequently, amphiphilic copolymer, with estimated structure of Poly(lactic acid)121-b-Poly(N-(3-aminopropyl)methacrylamide)103 (PLA121-b-PAPMA103) was obtained through the Reversible Addition Fragmentation chain Transfer (RAFT) reaction. The synthesized copolymer was self-assembled into spherical nanoparticles with size, Poly Dispersity Index (PDI) and zeta potential of 181.5 ± 21.3, 0.643 and of 44.9 ± 2.5 mV, respectively. The optimal copolymer/plasmid ratio was 4 with size, PDI and zeta potential of 161.7 ± 10.2, 0.277 and 36.5 ± 0.7, respectively for the delivery of short hairpin RNA (shRNA) plasmid against survivin. Additionally, the AS1411 aptamer was electrostatically decorated on the surface of the polyplex. In vitro studies on C26 cells revealed that the aptamer rendered nanoparticle transfer into the cell, dependent solely on the aptamer-receptor interactions. Lastly, in vivo studies involving tumor size and body weight change, survival and histological analysis indicated potential therapeutic index of the targeted nanoparticles with good safety profile.

Novel Nanoprobe with Combined Ultrasonography/Chemical Exchange Saturation Transfer Magnetic Resonance Imaging for Precise Diagnosis of Tumors.

Given that cancer mortality is usually due to a late diagnosis, early detection is crucial to improve the patient's results and prevent cancer-related death. Imaging technology based on novel nanomaterials has attracted much attention for early-stage cancer diagnosis. In this study, a new block copolymer, poly(ethylene glycol)-poly(l-lactide) diblock copolymer (PEG-PLLA), was synthesized by the ring-opening polymerization method and thoroughly characterized using Fourier transform infrared spectroscopy (FT-IR), proton nuclear magnetic resonance spectroscopy (H-NMR), X-ray diffraction (XRD), and thermogravimetric analysis (TGA). The obtained PEG-PLLA was used to prepare nanoparticles encapsulated with perfluoropentane and salicylic acid by the emulsion-solvent evaporation method, resulting in a new dual-mode nano-image probe (PEG-PLLA@SA·PFP). The zeta potential and mean diameter of the obtained nanoparticles were measured using dynamic light scattering (DLS) with a Malvern Zetersizer Nano. The in vitro biocompatibility of the PEG-PLLA nanoparticles was evaluated with cell migration, hemolysis, and cytotoxicity assays. Ultrasonic imaging was performed using an ultrasonic imaging apparatus, and chemical exchange saturation transfer (CEST) MRI was conducted on a 7.0 T animal scanner. The results of IR and NMR confirmed that the PEG-PLLA was successfully synthesized. The particle size and negative charge of the nanoparticles were 223.8 ± 2.5 nm and -39.6 ± 1.9 mV, respectively. The polydispersity of the diameter was 0.153 ± 0.020. These nanoparticles possessed good stability at 4 °C for about one month. The results of cytotoxicity, cell migration, and hemolysis assays showed that the carrier material was biocompatible. Finally, PEG-PLLA nanoparticles were able to significantly enhance the imaging effect of tumors by the irradiation of ultrasound and saturation by a radiofrequency pulse, respectively. In conclusion, these nanoparticles exhibit promising dual-mode capabilities for US/CEST MR imaging.

PH-Dependent Solution Micellar Structure of Amphoteric Polypeptoid Block Copolymers with Positionally Controlled Ionizable Sites.

While solution micellization of ionic block copolymers (BCP) with randomly distributed ionization sites along the hydrophilic segments has been extensively studied, the roles of positionally controlled ionization sites along the BCP chains in their micellization and resulting micellar structure remain comparatively less understood. Herein, three amphoteric polypeptoid block copolymers carrying two oppositely charged ionizable sites, with one fixed at the hydrophobic terminus and the other varyingly positioned along the hydrophilic segment, have been synthesized by sequential ring-opening polymerization method. The presence of the ionizable site at the hydrophobic segment terminus is expected to promote polymer association toward equilibrium micellar structures in an aqueous solution. The concurrent presence of oppositely charged ionizable sites on the polymer chains allows the polymer association to be electrostatically modulated in a broad pH range (ca. 2-12). Micellization of the amphoteric polypeptoid BCP in dilute aqueous solution and the resulting micellar structure at different solution pHs was investigated by a combination of scattering and microscopic methods. Negative-stain transmission-electron microscopy (TEM), small-angle neutron scattering (SANS), and small-angle X-ray scattering (SAXS) analyses revealed the dominant presence of core-shell-type spherical micelles and occasional rod-like micelles with liquid crystalline (LC) domains in the micellar core. The micellar structures (e.g., aggregation number, radius of gyration, chain packing in the micelle) were found to be dependent on the solution pH and the position of the ionizable site along the chain. This study has highlighted the potential of controlling the position of ionizable sites along the BCP polymer to modulate the electrostatic and LC interactions, thus tailoring the micellar structure at different solution pH values in water.

Poly lactic acid production using the ring opening polymerization (ROP) method using Lewis acid surfactant combined iron (Fe) catalyst (Fe(DS)3)

LASC catalyst synthesis process was carried out using iron metal (Fe) and its characterization properties were tested. There are five stages carried out, namely, the manufacture of the LASC Fe(DS)3 catalyst, lactic acid dehydration, polycondensation of lactic acid into l-lactic acid oligomers (OLLA), depolymerization of oligomers into l-lactide, and the ROP process to convert l-lactide into Polymers. l-lactic acid (PLLA). The analysis used is as follows, Karl-Fisher; Spectroscopy Fourier Transform Infrared (FTIR); and Nuclear Magnetic Resonance (HNMR); Gel Permeation Chromatography (GPC); Thermogravimetry Gravity Analysis (TGA) and X-Ray Diffraction (XRD). Based on the experimental results, the catalyst Fe(DS)3 has a crystallinity value of 24% which indicates an amorphous nature and is easy to react. The value of the thermal stability of the catalyst is at 180 °C where the catalyst is able to process up to a temperature of 180 °C. Each step of the ROP is validated by FTIR analysis which shows that the components of the group are in accordance with the expected product. The comparison of the crystallinity values of PLA produced with FeCl3 and Fe(DS)3 were 37.5 and 49%, respectively. Melting temperature (Tm) values are 111 and 107 °C, respectively, Td values are 327 and 352 °C, and the resulting molecular weights are 23,720 and 20,232 g/mol. Based on the results obtained, it can be seen that the use of a LASC catalyst in the form of Fe(DS)3 is more effective than without using a LASC catalyst.

Antimicrobial Properties of Biocompatible Poly (Ɛ-Caprolactone) Treated with Plant Extract

Poly (ɛ-caprolactone) (PCL) was synthesized using ethylene glycol initiator and catalyst accompanied by ring-opening polymerization method. The number average molecular weight (Mn) of the obtained polymer was found to be 4000 gmol-1. In addition, the characteristic signals of PCL were determined with Fourier-transform infrared spectroscopy (FT-IR). Decomposition temperatures were investigated by Thermogravimetric Analysis (TGA) and melting temperatures (Tm) were investigated by Differential Scanning Calorimetry (DSC). Tm of PCL at 57.3 °C was observed. PCL was treated with Rumex patientia L. ethanolic plant extract and its effects on Klebsiella pneumoniae ATCC 700603, Bacillus megaterium DSM32, Staphylococcus aureus ATCC25923, Escherichia coli ATCC25322, and Candida albicans FMC17 microorganisms were examined. It was determined that PCL, which did not show antimicrobial activity, showed antimicrobial activity on some microorganisms after being treated with the plant.

A Review on the Synthesis of Polypeptoids

Polyeptoids are a promising class of polypeptide mimetic biopolymers based on N-substituted glycine backbones. Because of the high designability of their side chains, polypeptoids have a wide range of applications in surface antifouling, biosensing, drug delivery, and stimuli-responsive materials. To better control the structures and properties of polypeptoids, it is necessary to understand different methods for polypeptoid synthesis. This review paper summarized and discussed the main synthesis methods of polypeptoids: the solid-phase submonomer synthesis method, ring-opening polymerization method and Ugi reaction method.

Precision Synthesis of Polypeptides via Living Anionic Ring-Opening Polymerization of N-Carboxyanhydrides by Tri-thiourea Catalysts.

The chemistry of α-amino acid N-carboxyanhydrides (NCAs) has a history of over 100 years, but precise and efficient ring-opening polymerization methods for NCAs remain highly needed to facilitate the studies of polypeptides─that is, mimics of natural proteins─in various disciplines. Moreover, the universally accepted NCA polymerization mechanisms are largely limited to the "amine" and the "activated monomer" mechanisms, and the anionic ring-opening polymerization of NCAs has so far not been invoked. Herein, we show an unprecedented anion-binding catalytic system combining tripodal tri-thiourea with sodium thiophenolate that enables the fast and selective anionic ring-opening polymerization of NCAs. This method leads to the precision construction of various polypeptides with living polymerization behavior and is evidenced by narrow molecular weight distributions (Mw/Mn < 1.2), chain extension experiments, and minimal "activated monomer" pathway. Calculations and experimental results elucidate a living anionic polymerization mechanism, and high selectivities for monomer propagation relative to other deleterious side reactions, such as the "activated monomer" pathway, are attributed to the enhanced stabilization of the propagating carbamate anion, which is enforced by an intramolecular hydrogen bond within the tri-thiourea structure.

Self-Assembly of Repetitive Segment and Random Segment Polymer Architectures.

Recent advances in chemical synthesis have created new methodologies for synthesizing sequence-controlled synthetic polymers, but rational design of monomer sequence for desired properties remains challenging. In this work, we synthesize periodic polymers with repetitive segments using a sequence-controlled ring-opening metathesis polymerization (ROMP) method, which draws inspiration from proteins containing repetitive sequence motifs. The repetitive segment architecture is shown to dramatically affect the self-assembly behavior of these materials. Our results show that polymers with identical repetitive sequences assemble into uniform spherical nanoparticles after thermal annealing, whereas copolymers with random placement of segments with different sequences exhibit disordered assemblies without a well-defined morphology. Overall, these results bring a new understanding to the role of periodic repetitive sequences in polymer assembly.

Influence of polymer molar mass and mixture stoichiometry on polyelectrolyte complexes of poly(l-arginine) and Poly(l-glutamic acid)

Poly(l-arginine) (PARG) and poly(l-glutamic acid) (PLGA) homopolypeptides were custom synthesized by precision N-carboxyanhydride ring-opening polymerization methods with two molar masses, matched for pairs of cationic and anionic polypeptides (degrees of polymerization n = 100 and n = 500). The conformations of the homopolypeptides were probed using circular dichroism (CD) and FTIR spectroscopy which revealed the presence of mainly polyproline II (PPII) conformation. Small-angle X-ray scattering (SAXS) showed concentration-dependent polyelectrolyte peaks and form factor with high q scaling due to the excluded volume behaviour of the wormlike chains. We then examined polyelectrolyte complexation in mixtures of pairs of PARG and PLGA polypeptides with matched molar masses. Precipitation was generally observed and the structures of precipitates, supernatant and resuspended precipitates were investigated using CD, SAXS and cryo-TEM. These revealed that, contrary to prior suggestions in the literature, the precipitates contain mostly polypeptides in a PPII-like conformation, and there is only a minimal β-sheet content (which is enhanced upon drying the sample during preparation for certain measurements). The precipitates have a fractal-like structure as revealed by cryo-TEM and SAXS. Our findings on the structure of polypeptide complex precipitates contribute to the understanding of phase separation of polyelectrolyte complexes and coacervation and may shed light on the formation of inter-cellular bodies of proteins and peptides such as Lewy and other inclusion bodies.

Effect of oligo(ethylene glycol) length on properties of poly(oligoethylene glycol terephthalate)s and their cyclic oligomers

We present here the effect of oligo(ethylene glycol) (OEG) segmental length on properties of cyclic oligo(oligoethylene glycol terephthalate)s (COEGTs) and their corresponding polymer counterparts, poly(oligoethylene glycol terephthalate)s (POEGTs). COEGT monomers were synthesized from terephthaloyl chloride with corresponding diethylene glycol, triethylene glycol, and tetraethylene glycol under pseudo-high-dilution conditions. As those large ring cyclic monomers are hard to be polymerized via traditional ring-opening polymerization, a cascade polycondensation-coupling ring-opening polymerization method is utilized to obtain high molecular weight POEGTs. The cascade polymerization mechanism is confirmed by the kinetics study. The structures of COEGTs and POEGTs were well characterized and their properties were studied to reveal the structure-property relationship. With the increment of OEG length in repeating units, the chain flexibility of POEGT and COEGTs is enhanced. As a result, the melting temperatures of COEGTs and glass transition temperatures of POEGTs decrease. On the other hand, the thermal degradation temperature of POEGTs and COEGTs increases due to the enhanced ether fraction and reduced ring strain. Solid-state polymer electrolytes based on POEGTs was prepared by blending with lithium bis(trifluoromethanesulfonyl)imide. The measured ionic conductivity increased with the OEG length in POEGT repeating units. Our results revealed the effect of OEG length on the structure-property relationship in cyclic oligo(ether ester)s and copoly(ether ester)s, providing a facile way to tune their properties.

Synthesis and properties of polyurethane acrylate oligomer based on polycaprolactone diol

Abstract The polycaprolactone diol (PCL diol) was prepared by ring-opening polymerization method, with hydroquinone bis(2-hydroxyethyl) ether as the reactive initiator and ε-caprolactone as the monomer. The polyurethane acrylate (PUA) was prepared with the self-made PCL diol. Then, PUA was used to prepare the ultraviolet curable coatings. The structure and molecular weight of PCL diol was characterized by Fourier transform infrared spectroscopy, gel-permeation chromatography, and hydroxyl value titration. The performance of the cured coating film was characterized by thermogravimetric analysis and scanning electron microscope. The flexibility and hardness of the cured coating film were tested. The results showed that the narrow molecular weight PCL diol was successfully synthesized. The UV curing coating film had the optimal performance with a hardness of 3H, flexibility of 1.5 mm, abrasion resistance of 0.028 g−1, and adhesion of grade 1, all coating films showed good thermal properties.

Synthesis and crystallization behavior of poly (lactide-co-glycolide)

Poly (lactide-co-glycolide) (PLGA) has emerged as an important material in tissue engineering. However, lactic acid (LA) produced during PLGA degradation is prone to inflammation, which is a shortcoming that must be avoided. To this end, a method for preparing crystalline PLGA is described here by using cross-linking nucleation. The pentaerythritol (PET), L-lactide and glycolide were first used to prepare the four-armed PLGA (4arm-PLGA) via the ring-opening polymerization (ROP) method. Such symmetrical four-armed PLGA was then grafted and crosslinked with N’N-methylenebisacrylamide (MBAM) simultaneously, and finally obtained the crystalline 4arm-PLGA (C4-PLGA-M). The C4-PLGA-M has controllable crystallinity, which could effectively control the degradation rate of PLGA. The C4-PLGA-M were characterized by POM and WAXS, and the accelerated degradation tests of C4-PLGA-M showed a sixfold increase at most in the degradation time compared to alone four-armed PLGA. The results of cell culture confirmed that the reduction of LA from hydrolysis process could be beneficial to the cell growth. Such crystalline C4-PLGA-M is expected to have ideal performance in tissue engineering.

Chemically recyclable thermoplastics from reversible-deactivation polymerization of cyclic acetals.

Identifying plastics capable of chemical recycling to monomer (CRM) is the foremost challenge in creating a sustainable circular plastic economy. Polyacetals are promising candidates for CRM but lack useful tensile strengths owing to the low molecular weights produced using current uncontrolled cationic ring-opening polymerization (CROP) methods. Here, we present reversible-deactivation CROP of cyclic acetals using a commercial halomethyl ether initiator and an indium(III) bromide catalyst. Using this method, we synthesize poly(1,3-dioxolane) (PDXL), which demonstrates tensile strength comparable to some commodity polyolefins. Depolymerization of PDXL using strong acid catalysts returns monomer in near-quantitative yield and even proceeds from a commodity plastic waste mixture. Our efficient polymerization method affords a tough thermoplastic that can undergo selective depolymerization to monomer.

Synthesis of Low Viscosity Polydimethylsiloxane Using Low Grade of Octamethylcyclotetrasiloxane

Polydimethylsiloxane (PDMS) has been widely used as a vitreous humour substitution in vitreoretinal surgery. Due to its limited availability and increasing domestic needs, the price of PDMS in Indonesia became very expensive. Previously, we reported the synthesized of PDMS from a high grade of monomer of 98% of Octamethylcyclotetrasiloxane (D4) and found that all PDMS samples produced high quality samples similar to that of commercial one. However, by considering the ease of obtaining raw materials and also the production costs, the synthesis of PDMS using monomer which easy to be found in Indonesia and low production costs is needed to be developed. Here, we reported the synthesis of PDMS using low grade of 96% of D4 in order to produce high quality of PDMS with low viscosity that can be used for vitreous humous substitution in vitreoretinal surgery. PDMS samples with low viscosity value of 0.94-1.35 Pa.s have been successfully synthesized from low grade of D4 and MM using ring-opening polymerization method. The yields of PDMS resulted in this research were in the range between 67.27% and 76.26%. From FTIR spectroscopy, it is found that all synthesized samples have structure and functional groups similar to PDMS using high grade of monomer of 98% Octamethylcyclotetrasiloxane (D4). From refractometer and surfgauge measurements, all samples have refractive index in the range of 1,4034-1,4040 and the value surface tension was 21 m.N/m.

Formulation, Process, and Scale-Up Engineering of Silicone Oil

After a successfully identified and synthesized Polydimethylsiloxane is known as silicone oil, the product needs to be upgraded and reformulated into a scalable dosage form. The scale-up in the production of silicone oil is very important in order to prepare the fabrication of silicone oil in large quantities. Here, we reported the synthesis of silicone oil using a duplicated scale to produce silicone oil of the same target quality as a laboratory scale. The dosage was increased twice compared to the previous report. The scale-up of silicone oil samples with viscosity values ​​of 1700 - 2920 mPa.s has been successfully synthesized from Octamethylcyclotetrasiloxane (D4) as monomer and Hexamethyldisiloxane (MM) as terminator using ring-opening polymerization method. From FTIR spectroscopy, it was found that all the samples synthesized with double dosage had a structure and functional groups similar to commercial PDMS. From the refractometer and surfgauge measurements, the scale-up sample has a refractive index in between 1.4026 and 1.4038 and a surface tension value from 19.0 to 20.0 m.N/m.

Influence of miscible and immiscible sequences of poly(D-lactide) copolymers on the competition of stereocomplex- and homo-crystallization in poly(L-lactide) blends

A high molecular weight (HMw) PLLA has been blended with a low molecular weight (LMw) PDLA and its two types diblock copolymers (PEG-b-PDLA and PDMS-b-PDLA), respectively, to investigate the stereocomplex (sc) and homochiral (hc) crystallization behaviors. The miscible PEG and immiscible PDMS segments with comparable molecular weight were introduced into PDLA by bulk ring-opening polymerization method. Compared to PLLA/PDLA, the introduction of both sequences could inhibit the crystallization kinetics of sc and hc crystallites of the blends due to the dilution effect of LMw segments. The formation of sc crystallites is prior to its hc counterparts. The shorter induction period of hc crystallites of PLLA/PEG-b-PDLA blend indicates that the miscible PEG segments could promote the mobility of PLLA chains. Due to the involving of PEG chains, the spherulite exhibits coarsen and irregular texture and its lamellae show sparse string-like structure. The microphase separation between PLA and PDMS segments as evidenced by SAXS results in the increased sc nuclei and different growth mode of hc crystallites. The phase separated microdomains weakened the competition between sc and hc crystallites, and the former acts as a template for repeated assembly of the latter. X-ray analysis also reveal that sc crystallites possess much thicker lamellar thickness than hc crystallites in PLLA/PDLA and PLLA/PEG-b-PDLA blends.

Spectral, thermal and morphological studies of fluorescent dye grafted diblock copolymers

The preparation of the fluorescent diblock copolymer was carried out between poly(tetrahydrofuran) (PTHF) and poly(ε-caprolactone) (PCL) via bulk and ring-opening polymerization (ROP) method by using two different dyes such as fluorescent methyl red (MR) and eosin b (EB) as lone chemical initiators at 160 °C under N2 atmosphere for two hours. All the prepared homopolymer and diblock copolymer were examined by NMR and FT-IR like analytical instruments. The molecular weight of the diblock copolymer was higher than the homopolymer. The TGA results showed that the thermal stability of PTHF in the diblock copolymer was lower when compared with dye end capped PCL. In this work, the ROP efficiency of two different dye-based initiators is compared and their results are critically analyzed. The –OH group-containing EB exhibited excellent results. The dye conjugated polymer was prepared by a single-step process.