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Articles by Yodthong Baimark
Total Records ( 11 ) for Yodthong Baimark
  Yodthong Baimark , Yaowalak Srisuwan , Nuanchai Kotsaeng and Theeraphol Phromsopha
  Methoxy poly(ethylene glycol)-b-poly(ε-caprolactone-co-D,L-lactide) diblock copolymers [MPEG-b-P(CL-co-DLL)] were synthesized by ring-opening polymerization of CL and DLL using MPEG with molecular weight of 5,000 g mol-1 and stannous octoate as the initiating system. Surfactant-free and core-shell nanoparticles of MPEG-b-P(CL-co-DLL) were prepared by modified-spontaneous emulsification solvent diffusion method without any surfactants. Influences of CL:DLL ratio of the diblock copolymers on nanoparticle characteristics were investigated and discussed. The sizes of colloidal nanoparticles obtained from light-scattering analysis were in the range of 84-639 nm. The nanoparticle size decreased with increasing the DLL ratio. Scanning and transmission electron micrographs indicated that the nanoparticles were spherical in shape and smooth surface. Core-shell structure of the nanoparticles consisting of the hydrophilic outer shell of MPEG and the hydrophobic inner core of P(CL-co-DLL) was confirmed by 1H-NMR spectroscopy.
  Yodthong Baimark
  Aim of this research is to prepare organic solvent and surfactant-free microspheres of biodegradable methoxy poly(ethylene glycol)-b-poly(ε-caprolactone) diblock copolymer. The microspheres were produced in 90-100°C glycerol by melt dispersion method. Morphology of the microspheres was spherical in shape with rough surfaces. Almost microspheres were in the size range of 300-500 μm. Microsphere cross-sections showed condensed phases throughout the microsphere matrices. Melting temperatures and heats of melting of the MPEG-b-PCL were decreased in the microsphere form. In conclusion, the use of melt dispersion method results in organic solvent and surfactant-free biodegradable microspheres of diblock copolymer that showing a potentially useful drug delivery systems with free from surfactants and organic solvents.
  Yodthong Baimark and Yaowalak Srisuwan
  Background and Objective: Bio-renewable and biodegradable stereo complex polylactides (scPLs) have widely investigated for use as high-performance bioplastic products. However, melt process ability and brittleness of the scPL were limited for this purpose. In this study, physicochemical and mechanical properties of scPL/poly(ε-caprolactone-co-L-lactide) copolyester blends with and without chain extension were determined. Materials and Methods: The scPL/copolyester blend pellets were prepared by in situ melt blending of poly(L-lactide), poly(D-lactide) and copolyester. The influences of the copolyester ratios (100/0, 90/10, 80/20 and 60/40 w/w) and chain extension on the characteristics of the scPL pellets, including stereo complex formation, thermal stability, melt flow index (MFI) and their film forming were determined. Properties of the compressed blend films were also investigated. Results: The copolyester blending enhanced the stereo complexation of the blend pellets. The MFI of the blend pellets increased with the copolyester ratio. The continuous and smooth blend films were successfully prepared using a compression molding technique when the copolyester ratio was increased up to 20% wt. The compression force also enhanced the stereo complexation of the blend films. The chain extension improved the phase compatibility of the scPL/copolyester blend films. The flexibility of the blend films slightly improved as the copolyester ratio increased. Conclusion: This study could provide a new insight into the synergistic effects of copolyester blending, chain extension and compression force for designing high-performance scPL products with controllable film forming and flexibility.
  Yodthong Baimark , Supasin Pasee , Wuttipong Rungseesantivanon and Natcha Prakymoramas
  Background and Objective: Poly (L-lactide) (PLLA) is a biodegradable bioplastic that has attracted much attention for use in biomedical and packaging applications. In this work, effect of chain extender on thermal and mechanical properties of injection-molded PLLA-b-poly (ethylene glycol)-b-PLLA triblock copolymer (PLLA-PEG-PLLA) and their comparison with the injection-molded PLLA were investigated. Materials and Methods: A flexible PLLA-PEG-PLLA was adjusted by changing its Melt Flow Index (MFI) by chain-extension reaction before injection molding. Differential scanning calorimeter was used to investigate the thermal properties. The mechanical properties of injection-molded PLLA and PLLA-PEG-PLLA were determined by universal testing machine for tensile and flexural properties, impact tester and hardness testers. One-way analysis of variance and Duncan’s multiple test (p<0.05) were used to assess data. Results: The addition of chain extender decreased the MFI of PLLA-PEG-PLLA. The chain-extended PLLA-PEG-PLLA exhibited faster crystallization and more hydrophilicity than the PLLA. Hydrophilicity of PLLA-PEG-PLLA increased with the chain-extender content. From tensile curves, the chain-extended PLLA-PEG-PLLA had a yield effect indicating they were flexible. Strain at break and impact strength of chain-extended PLLA-PEG-PLLA were higher than the PLLA while their flexural stress and hardness were lower. The crystallization behaviors and mechanical properties of PLLA-PEG-PLLA did not change with the chain-extender content. Conclusion: The injection-molded bioplastics with high flexibility and toughness could be fabricated from chain-extended PLLA-PEG-PLLA.
  Yaowalak Srisuwan , Mangkorn Srisa-ard , Chaiyasit Sittiwet , Yodthong Baimark , Nual- Anong Narkkong and Chirapha Butiman
  Nanocomposite and nanoporous silk fibroin (SF) films were prepared by film casting of SF solution containing surfactant-free colloidal nanoparticles of methoxy poly (ethylene glycol)-b-poly (D, L-lactide) diblock copolymer (MPEG-b-PDLL). Self-condensation and nanophase separation of the nanoparticles from SF film matrix during film drying process gave nanopore structures. The colloidal nanoparticles were prepared in SF solution by modified-spontaneous emulsification solvent diffusion method without any surfactant. The interaction between SF and MPEG-b-PDLL in nanocomposite films was studied by Fourier transform infrared spectroscopy and thermogravimetry. The film transparency of SF nanocomposite films decreased as increasing the MPEG-b-PDLL ratio. Scanning Electron Microscopy (SEM) results indicated that the nanoparticle sizes in the films were in the range of 50-200 nm with spherical shape. Nanopore structures with pore size of less than 150 nm can be observed from SEM images of the film surface and cross-section. The nanopores are interconnected throughout the nanocomposite films. The number and size of nanoparticles and nanopores increased when the MPEG-b-PDLL ratio was increased.
  Yodthong Baimark
  Aims of this study were to synthesize methoxy poly (ethylene glycol)-b-poly (ε-caprolactone) diblock copolymers (MPEG-b-PCL) and to prepare their surfactant-free nanospheres by modified-spontaneous emulsification solvent diffusion method for controlled release delivery of hydrophobic drug. Ibuprofen was used as a poorly-water soluble model drug. Influences of PCL block length and drug loading content on nanosphere characteristics and drug release behaviors were evaluated. The prepared nanospheres with and without drug loading were found of spherical shape and smooth surface with size less than 150 nm. FTIR spectroscopy and differential scanning calorimetry studies showed the interactions between ibuprofen and MPEG-b-PCL had occurred, suggesting the well distribution of ibuprofen into nanosphere matrices. An increase in the PCL block length led to a decrease in drug encapsulation efficiency. The drug release profiles were biphasic with a fast burst release followed by a slow one. The drug release rates from the MPEG-b-PCL nanospheres strongly depended on the PCL block length and the drug loading content.
  Yodthong Baimark and Prasong Srihanam
  Silk Fibroin (SF) microparticles containing hollow structure were prepared by a water-in-oil emulsion solvent diffusion method without any surfactants. Aqueous SF solution and ethyl acetate were used as water and oil phases, respectively. Influences of SF concentration and post methanol treatment on microparticle characteristics were investigated. All microparticles contained open hollow structures. Microparticle sizes increased with the SF concentration. Conformation of SF microparticles determined from FTIR spectra changed from predominantly random coil to β-sheet form after methanol treatment. Particle surfaces of methanol-treated SF microparticles were rougher than those of non-treated. The SF concentrations and methanol treatment did not affect open hollow structure of the SF microparticles. Major advantages of this method are the elimination of surfactants and extractable pore templates. These hollow SF microparticles are expected to be potential used as biodegradable microcarriers of cell and protein drug, because their hollow structures should permit cell attachment and enzyme immobilization.
  Mangkorn Srisa-ard and Yodthong Baimark
  Influences of arm number and arm length of poly(D,L-lactide)s (PDLLs) on their thermal properties were investigated. The PDLLs with linear (1 arm) and star (4, 6 and 16 arms) shapes were synthesized via ring-opening polymerization of DLL monomer in bulk at 130°C for 24 h under nitrogen atmosphere. Stannous octoate was used as a catalyst. Initiators containing hydroxyl end groups of 1, 4, 6 and 16 were chosen as core molecules for synthesizing 1-, 4-, 6- and 16-armed PDLLs, respectively. Thermal properties of the PDLLs observed from their differential scanning calorimetric and thermogravimetric thermograms strongly depended upon their arm numbers and arm lengths. For the same DLL/initiator ratio (208/1 by mole), glass transition temperatures (Tg) and temperatures of maximum decomposition rate (Td, max) of the PDLLs decreased when the arm length decreased (or arm number increased). For similar PDLL arm lengths (4,500 and 4,900 g moL-1 for 6-armed star-shaped and 1-armed linear PDLLs, respectively), the Tg and Td, max of star-shaped PDLL was higher than that of the linear PDLL.
  Yodthong Baimark
  The objective of this research was to investigate the effect of arm number of Poly(l-lactide)-b-methoxy poly(ethylene glycol) (PLL-b-MPEG) amphiphilic diblock copolymers on their characteristics of drug-loaded nanoparticles and in vitro drug release. Linear and star-shaped PLL-b-MPEG diblock copolymers were synthesized via the ring-opening polymerization of L-lactide followed by coupling reaction with a monofunctional carboxyl end-group MPEG. These diblock copolymers included linear copolymer having one arm and star-shaped copolymers having four and six arms. The crystallinity of MPEG block within diblock copolymers was suppressed. The melting point (Tm) and degree of crystallinity (χc) of PLL block within diblock copolymers decreased as the arm number increased. Drug-loaded nanoparticles of these copolymers were prepared by the emulsification-diffusion method under surfactant-free condition. Indomethacin was used as a poorly water-soluble model drug. The nanoparticles with less than 200 nm in size were nearly spherical shape. Different arm numbers did not affect average size and drug loading efficiency. However, the Tm and χc of diblock copolymers slightly decreased after drug loading. From in vitro drug release test, drug release content increased steadily as the arm number increased.
  Yodthong Baimark and Yaowalak Srisuwan
  Poly(L-lactide) (PLL) is an environmentally friendly polymer that has widely been used in medical and packaging applications because of its biodegradability and biocompatibility. Star-shaped PLLs are expected to exhibit different properties compared to the linear PLL. The objective of this study was to investigate the effects of blend ratios and blending techniques including single step ring-opening polymerization and solution blending on the characteristics of linear (1-arm)/star-shaped (6-arm) PLL blends. A 1-dodecanol/ dipentaerythritol mixture and stannous octoate were used as an initiating system. Intrinsic viscosity, glass transition temperature and crystallizing temperature of the PLL blends steadily increased, while heat of crystallization and heat of melting significantly decreased when the star-shaped blend ratio was increased. However, melting temperature and thermal decomposition did not change. Mechanical properties of the PLL films were also influenced by the blend ratio. The physical and mechanical properties of the PLL blends obtained from single step polymerization depend upon the blend ratio, similar as when they are obtained from the solution blending method.
  Supawut Khamhan and Yodthong Baimark
  The objective of this study was to prepare biodegradable chitosan nanocomposite films contained dispersed nanoparticles of methoxy poly(ethylene glycol)-b-poly(ε-caprolactone) (MPEG-b-PCL) or methoxy poly(ethylene glycol)-b-poly(D,L-lactide) (MPEG-b-PDLL) diblock copolymers by solvent evaporation of nanoparticle suspension-chitosan solution. The nanoparticles were firstly produced in the chitosan solution by modified-spontaneous emulsification solvent diffusion method without any surfactants before film casting. The dispersed nanoparticles with approximately 100 and 300 nm in sizes for MPEG-b-PDLL and MPEG-b-PCL, respectively can be observed throughout the chitosan film matrices. Nanoparticle morphology was spherical shapes with smooth surfaces. The nanoparticles of MPEG-b-PDLL were smaller than the MPEG-b-PCL. The possible interactions between the chitosan film matrices and the nanoparticles were evaluated by thermogravimetry. Thermal stability of the chitosan film matrices were enhanced by nanoparticle incorporating. The chitosan/MPEG-b-PCL nanocomposite films had lower film transparency and moisture uptakes than the chitosan/MPEG-b-PDLL nanocomposite films. The both film transparency and moisture uptakes decreased as the diblock copolymer ratio increased.
 
 
 
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