Removal of bacteria from water by systems based on insoluble polystyrene–polyethyelnimine

A study was made of the removal of viable bacterial cells from sterilized physiological saline (saline) by insoluble polymer beads. The polymers (CMPS–PEI300 and CMPS–PEI600) were prepared by reactions of chloromethylated, divinylbenzene crosslinked polystyrene (CMPS) beads with polyethyleneimines (PEI) (MW = about 300 and 600). The bacterial strain cells used were Escherichia coli (E. coli), Staphylococcus aureus (S. aureus), and Pseudomonas aeruginosa (P. aeruginosa). Decrease coefficients (D, which corresponds to adsorption rate constant) for the viable cell numbers of E. coli by CPMS–PEI300 and CMPS–PEI600 were 28 and 120 (mL/gh) in saline, respectively. These D's were less than those (72 and 270 mL/gh) in sterilized, distilled, and deionized water (sterilized water). The D's for S. aureus and P. aeruginosa by CMPS–PEI600 were 46 and 76 (mL/g h), respectively. The D for E. coli by CMPS–PEI600 was compared with R (removal coefficient) for that by pyridinium type polymers. Bactericidal activity of PEI600 was examined on E. coli and P. aeruginosa in saline. Also, that of poly(ethylene glycol) 600 was done on E. coli in saline.     

Amphiphilic linear–hyperbranched polymer poly(ethylene glycol)–branched polyethylenimine–poly(ϵ‐caprolactone): synthesis,self‐assembly and application as stabilizer of platinum nanoparticles

Amphiphilic linear–hyperbranched polymer poly(ethylene glycol)–branched polyethylenimine–poly(?‐caprolactone) (PEG‐PEI‐PCL) was synthesized by progressively conjugating PEG (one chain) and PCL (multi‐chains) to PEI (hyperbranched architecture) with a yield of 87%. PEG‐PEI‐PCL forms nano‐sized uniform spherical micelles by self‐assembly in water. The micelles had an average diameter of 56 nm determined using dynamic light scattering and 35 nm observed from transmission electron microscopy images. PEG‐PEI‐PCL was used as a stabilizer of platinum nanoparticles (PtNPs) for the first time. The particle diameter of PEG‐PEI‐PCL‐stabilized PtNPs was 7.8 ± 1.4 nm. Amphiphilic (hydrophilic–hydrophilic–hydrophobic) and hyperbranched (linear–hyperbranched–grafted) structures enabled PtNPs to effectively stabilize and disperse in liquid‐phase synthesis. The highly disperse PtNPs in PEG‐PEI‐PCL micelles improved the catalytic activity for the reduction of 4‐nitrophenol with a catalytic yield of near 100%. © 2016 Society of Chemical Industry     

Grafting onto carbon black by the reaction of reactive carbon black having acyl chloride group with several polymers

Summary Acyl chloride group introduced onto carbon black rapidly lost its activity by the moisture in air. However, the decrease of acyl chloride group content in vacuum was negligibly small. By the reaction of the acyl chloride group with several polymers having hydroxyl or amino group, such as polyethylene glycol (PEG), poly(vinyl alcohol)(PVA), and polyethyleneimine (PEI), these polymers were found to be effectively grafted onto carbon black; for instance, the grafting ratio of PEG (Mn=8.2×10³), PVA (Mn=2.2×10⁴), and PEI (Mn=2.0×10⁴) was 18.5%, 32.9%, and 45.8%, respectively. The number of polymer grafted onto carbon black decreased with an increase of its molecular weight.     

Minimizing the surface effect of PDMS–glass microchip on polymerase chain reaction by dynamic polymer passivation

Polydimethyl siloxane (PDMS)–glass microchip has a very strong surface effect on polymerase chain reaction (PCR), leading to a very poor PCR yield. In the work reported here, practical dynamic passivation of surfaces of PDMS–glass microchip using polyethylene glycol (PEG) or polyvinylpyrrolidone (PVP) was achieved using a conventional thermocycler. The passivation procedure was cost‐effective and easy to conduct. The effects of polymer molecular weight and polymer concentration on tube PCR efficiency were investigated primarily to prescreen out suitable polymers and polymer concentrations in the PCR mixture. The result from tube PCR indicated that both PEG and PVP could affect the performance of Taq polymerase. A final concentration of 0.025% (w/v) or 0.4% (w/v) polymer in the PCR mixture can enhance the tube PCR, while 1% (w/v) polymer was found to inhibit the reaction. PEG was more effective in tube PCR, although PVP performed better in chip PCR. Instead of employing the polymer directly in the PCR mixture, i.e. the conventional in situ passivation approach, another approach of dynamic passivation by pre‐injecting polymers into the microchip achieved better performance. The efficiency of pre‐passivation was found to follow the order: PVP10000>PVP55000, PEG8000> PEG10000>PEG400. After pre‐passivation with PVP10000, PVP55000 and PEG8000, the PCR efficiency can recover to 93%, 86% and 83%, respectively, of that obtained from tube PCR. Copyright © 2006 Society of Chemical Industry     

Macroporous bead modification with polyethylenimines of different molecular weights as polycationic ligands

Polyethylenimines (PEIs) with different molecular weights [number‐average molecular weights (M_n′s) = 60,000, 1200, and 423] were coupled onto macroporous beads. These rigid and spherical beads were prepared by the crosslinking of 2‐hydroxyethyl methacrylate and ethylene glycol dimethacrylate. The PEI attachment was carried out through epoxy groups yielded in a previous activation step with epichlorohydrin on matrix hydroxyl groups. Different initial concentrations of PEI were assayed. The supports so obtained were characterized by several techniques (Fourier transform infrared spectroscopy, scanning electron microscopy, thermogravimetric analysis, and mercury intrusion porosimetry). All of the PEI‐containing beads were used to analyze the influence that the molecular weight, the shape of the polycationic ligand (PEI), and the degree of coupling onto the matrices may have had on the efficiency of the retention of the bovine serum albumin protein used as a model biomolecule. In these assays, the PEI‐modified beads with M_n = 60,000 showed better results than those modified with PEIs with M_n's of 1200 and 423. The presence of sparse and long chains of PEI 60,000 onto the matrix, by reason of their highest accessibility toward the large protein, may have resulted in a better disposition of functional groups, whereas more short chains in the other PEIs (M_n's = 1200 and 423) used as ligands would not have. © 2010 Wiley Periodicals, Inc. J Appl Polym Sci, 2010     

Grafting of branched polymers onto nano-sized silica surface: Postgrafting of polymers with pendant isocyanate groups of polymer chain grafted onto nano-sized silica surface

To control the surface wettability of nano-sized silica surface, the postgrafting of hydrophilic and hydrophobic polymers to grafted polymer chains on the surface was investigated. Polymers having blocked isocyanate groups were successfully grafted onto nano-sized silica surface by the graft copolymerization of methyl methacrylate (MMA) with 2-(O-[1′-methylpropylideneamino]caboxyamino)ethyl methacrylate (MOIB) initiated by azo groups previously introduced onto the surface. The blocked isocyanate groups of poly(MMA-co-MOIB)-grafted silica were stable in a desiccator, but isocyanate groups were readily regenerated by heating at 150 °C. The hydrophilic polymers, such as poly(ethylene glycol) (PEG) and poly(ethyleneimine) (PEI), were postgrafted onto the poly(MMA-co-MOIB)-grafted silica by the reaction of functional groups of PEG and PEI with pendant isocyanate groups of poly(MMA-co-MOI)-grafted silica to give branched polymer-grafted silica. The percentage of grafting increased with increasing molecular weight of PEG, but the number of postgrafted chain decreased, because of steric hindrance. The hydrophobic polymers, such as poly(dimethylsiloxane) were also postgrafted onto poly(MMA-co-MOI)-grafted silica. It was found that the grafting of hydrophobic polymer and the postgrafting of hydrophilic polymer branches readily controls the wettability of silica surface to water.     

Thermal analysis and non‐isothermal kinetics of poly(ethylene glycol) with different molecular weight

This study focuses on comprehensively investigating polyethylene glycol (PEG) with different molecular weight. Thermal properties of the PEGs were investigated by differential scanning calorimetry (DSC), as well as gradual melting and freezing tests with thermocouples. Results show that the degree of PEG crystallization increased with the increasing of the molecular weight of polymers. The temperatures of pure PEG 1000 and PEG 1000‐PEG 600 blends ranged from 20 to 50°C. The apparent activation energy of pure PEG1000 was 300 kJ/mol, whereas that of the PEG blend was 239 kJ/mol. During the crystallization process, Avrami index n ranged from 5 to 3 and half‐crystallization time t_1/2 decreased with the acceleration of the crystallization rate R. This difference was due to the increase in polydispersity of the PEG system and decrease in the degree of crystallization. POLYM. ENG. SCI., 54:2872–2876, 2014. © 2014 Society of Plastics Engineers     

New antimicrobial polyurea: Synthesis,characterization, and antibacterial activities of polyurea‐containing thiosemicarbazide–metal complexes

A novel class of polymer–metal complexes was prepared by the condensation of a polymeric ligand with transition‐metal ions. The polymeric ligand was prepared by the addition polymerization of thiosemicarbazides with toluene 2,4‐diisocyanate in a 1 : 1 molar ratio. The polymeric ligand and its polymer–metal complexes were characterized by elemental analysis, thermogravimetric analysis, Fourier transform infrared spectroscopy, and ¹³C‐NMR and ¹H‐NMR spectroscopy. The geometries of the central metal ions were determined by electronic spectra (UV–visible) and magnetic moment measurement. The antibacterial activities of all of the synthesized polymers were investigated against Bacillus subtilis and Staphylococcus aureus (Gram positive) and Escherichia coli and Salmonella typhi (Gram negative). These compounds showed excellent antibacterial activities against these bacteria with the spread plate method on agar plates, and the number of viable bacteria were counted after 24 h of incubation period at 37°C. The antibacterial activity results revealed that the Cu(II) chelated polyurea showed a higher antibacterial activity than the other metal‐chelated polyureas. © 2008 Wiley Periodicals, Inc. J Appl Polym Sci, 2008     

Antimicrobial poly(N‐vinyl‐2‐pyrrolidone‐alt‐maleic anhydride)/poly(ethylene imine) macrocomplexes

The antimicrobial polymer/polymer macrocomplexes were synthesized by radical alternating copolymerization of N‐vinyl‐2‐pyrrolidone with maleic anhydride [poly(VP‐alt‐MA)] with 2,2′‐azobis‐isobutyronitrile as an initiator at 65°C in dioxane solutions under nitrogen atmosphere, and interaction of prepared copolymer with poly(ethylene imine) (PEI) in aqueous solutions. The susceptibility of some Gram‐negative (Salmonella enteritidis and Escherichia coli) and Gram‐positive (Staphylococcus aureus and Listeria monocytogenes) bacteria to the alternating copolymer and its PEI macrocomplexes with different compositions in microbiological medium was studied using pour‐plate technique. All the studied polymers, containing biologically active moieties in the form of ionized cyclic amide, and macrobranched aliphatic amine groups and acid/amine complexed fragments, were more effective against L. monocytogenes than those for Gram‐positive S. aureus bacterium. This fact was explained by different surface layer structural architectures of biomacromolecules of tested bacteria. The resulting polymeric antimicrobial materials are expected to be used in various areas of medicine and food industry. © 2006 Wiley Periodicals, Inc. J Appl Polym Sci 102:5841–5847, 2006     

Competitive hydrogen bonding mechanisms underlying phase behavior of triple poly(N‐vinyl pyrrolidone)–poly(ethylene glycol)–poly(methacrylic acid‐co‐ethylacrylate) blends

Differential scanning calorimetry (DSC) of triple blends of high molecular weight poly(N‐vinyl pyrrolidone) (PVP) with oligomeric poly(ethylene glycol) (PEG) of molecular weight 400 g/mol and copolymer of methacrylic acid with ethylacrylate (PMAA‐co‐EA) demonstrates partial miscibility of polymer components, which is due to formation of interpolymer hydrogen bonds (reversible crosslinking). Because both PVP and PMAA‐co‐EA are amorphous polymers and PEG exhibits crystalline phase, the DSC examination is informative on the phase state of PEG in the triple blends and reveals a strong competition between PEG and PMAA‐co‐EA for interaction with PVP. The hydrogen bonding in the triple PVP–PEG–PMAA‐co‐EA blends has been established with FTIR Spectroscopy. To evaluate the relative strengths of hydrogen bonded complexes in PVP–PEG–PMAA‐co‐EA blends, quantum‐chemical calculations were performed. According to this analysis, the energy of H‐bonding has been found to diminish in the order: PVP–PMAA‐co‐EA–PEG(OH) > PVP–(OH)PEG(OH)–PVP > PVP–H₂O > PVP–PEG(OH) > PMAA‐co‐EA–PEG(? O? ) > PVP–PMAA‐co‐EA > PMAA‐co‐EA–PEG(OH). Thus, most stable complexes are the triple PVP–PMAA‐co‐EA–PEG(OH) complex and the complex wherein comparatively short PEG chains form simultaneously two hydrogen bonds to PVP carbonyl groups through both terminal OH‐groups, acting as H‐bonding crosslinks between longer PVP backbones. © 2007 Wiley Periodicals, Inc. J Appl Polym Sci 2007     

12‐crown‐4–ether and tri(ethylene glycol) dimethyl–ether plasma‐coated stainless steel surfaces and their ability to reduce bacterial biofilm deposition

It has been demonstrated that surfaces coated with poly(ethylene glycol) (PEG) are capable of reducing protein adsorption, bacterial attachment, and biofilm formation. In this communication cold‐plasma–enhanced processes were employed for the deposition of PEG‐like structures onto stainless steel surfaces. Stainless steel samples were coated under 1,4,7,10‐tetraoxacyclododecane (12‐crown‐4)–ether and tri(ethylene glycol) dimethyl ether (triglyme)–radio frequency (RF)–plasma conditions. The chemistry and characteristics of plasma‐coated samples and biofilms were investigated using electron spectroscopy for chemical analysis (ESCA), atomic force microscopy (AFM), and water contact angle analysis. ESCA analysis indicated that the plasma modification resulted in the deposition of PEG‐like structures, built up mainly of –CH₂? CH₂? O– linkages. Plasma‐coated stainless steel surfaces were more hydrophilic and had lower surface roughness values compared to those of unmodified substrates. Compared to the unmodified surfaces, they not only significantly reduced bacterial attachment and biofilm formation in the presence of a mixed culture of Salmonella typhimurium, Staphylococcus epidermidis, and Pseudomonas fluorescens but also influenced the chemical characteristics of the biofilm. Thus, plasma deposition of PEG‐like structures will be of use to the food‐processing and medical industries searching for new technologies to reduce bacterial contamination. © 2001 John Wiley & Sons, Inc. J Appl Polym Sci 81: 3425–3438, 2001     

Synthesis and characterization of new optically active poly(amide‐imide‐urethane) thermoplastic elastomers,derived from 4,4′‐(hexafluoroisopropylidene)‐N,N′‐bis(phthaloyl‐L‐leucine‐p‐aminobenzoic acid) and PEG‐MDI

A new class of optically active poly(amide‐imide‐urethane) was synthesized via two‐step reactions. In the first step, 4,4′‐methylene‐bis(4‐phenylisocyanate) (MDI) reacts with several poly(ethylene glycols) (PEGs) such as PEG‐400, PEG‐600, PEG‐2000, PEG‐4000, and PEG‐6000 to produce the soft segment parts. On the other hand, 4,4′‐(hexafluoroisopropylidene)‐N,N′‐bis(phthaloyl‐L ‐leucine‐p‐amidobenzoic acid) (2) was prepared from the reaction of 4,4′‐(hexafluoroisopropylidene)‐N,N′‐bis(phthaloyl‐L ‐leucine) diacid chloride with p‐aminobenzoic acid to produce hard segment part. The chain extension of the above soft segment with the amide‐imide 2 is the second step to give a homologue series of poly(amide‐imide‐urethanes). The resulting polymers with moderate inherent viscosity of 0.29–1.38 dL/g are optically active and thermally stable. All of the above polymers were fully characterized by IR spectroscopy, elemental analyses, and specific rotation. Some structural characterization and physical properties of this new optically active poly(amide‐imide‐urethanes) are reported. © 2003 Wiley Periodicals, Inc. J Appl Polym Sci 91: 2288–2294, 2004     

Polyethylene glycol‐polyethylenimine‐tetrachloroplatinum (IV): A novel conjugate with good abilities of antitumor and gene delivery

It is much importance to develop novel multifunctional delivery systems for the combination therapy of drug and gene. In this work, a novel conjugate, polyethylene glycol‐polyethylenimine‐tetrachloroplatinum (IV) (PEG‐PEI‐Pt), with good abilities of antitumor and gene delivery was proposed by combining PEG (Mw 3400 Da), low molecular weight PEI (Mw 800 Da), and tetrachloroplatinum (IV). The antitumoral and gene transfection activities of PEG‐PEI‐Pt were analyzed in many tumor (A549, A375, HepG‐2, HuH‐7, and B16 cells) and normal (COS‐7 cells) cell lines. Similar to cisplatin (one platinum anticancer drug), PEG‐PEI‐Pt showed much higher sensitivity in tumor cells than in normal cells. More importantly, PEG‐PEI‐Pt had a potential to treat drug‐resistant tumors. Almost no transfection efficiency was observed for PEI (Mw 800 Da) and PEG‐PEI. Very interestingly, PEG‐PEI‐Pt could condense plasmid DNA efficiently, and exhibited good transfection efficiency in B16, HepG‐2, A375 and COS‐7 cells, comparable to even higher than PEI 25 kDa. In addition, PEG‐PEI‐Pt could also effectively deliver siRNA into the cytoplasm of tumor cells. With the good antitumoral and gene delivery abilities, PEG‐PEI‐Pt may have a great potential for combination therapy of drug and gene. © 2011 Wiley Periodicals, Inc. J Appl Polym Sci, 2012     

The nanocomposites of zinc oxide/L‐amino acid‐based chiral poly(ester‐imide) via an ultrasonic route: Synthesis,characterization, and thermal properties

In this investigation, a chiral poly) ester‐imide) (PEI) via direct polyesterification of N,N′‐(pyromellitoyl)‐bis‐(L ‐tyrosine dimethyl ester) and N‐trimellitylimido‐L ‐methionine was prepared using the tosyl chloride/pyridine/N,N′‐dimethylformamide system as a condensing agent. This approach allows the insertion of two natural amino acids into the polymer backbone and the creation of a bioactive polymer. From the chemical point of view, the ester groups impart to the polymer's main and side chain increased sensibility to hydrolysis that can cause chain breaking. Therefore, this polymer is expected to be biodegradable and could be classified as an eco‐friendly polymer. The polymer also had a useful level of thermal stability associated with excellent solubility. PEI/zinc oxide bionanocomposites were subsequently prepared by an ultrasonic method as a simple and inexpensive route, using ZnO nanoparticles (ZnO‐NPs) modified by 3‐aminopropyltriethoxylsilane (KH550) as a coupling agent. The structure and properties of the obtained BNC polymers were confirmed by Fourier transform infrared spectroscopy, X‐ray diffraction, field emission scanning electron microscopy (FE‐SEM), transmission electron microscopy (TEM), and thermogravimetric analysis (TGA). The direct proofs for the formation of the true BNC polymers were provided by TEM. Also, the morphology study of the synthesized polymer‐based BNCs showed well‐dispersed ZnO‐NPs in the polymer matrix by FE‐SEM analysis. TGA studies indicated that an increase of the NP content led to an enhancement of the thermal stability of the new BNC polymers. © 2012 Wiley Periodicals, Inc. J Appl Polym Sci, 2012     

Synthesis and structural characterization of novel bionanocomposite poly(ester-imide)s containing TiO2 nanoparticles, S-valine, and l-tyrosine amino acids moieties

The incorporation of different percents of titanium dioxide (TiO₂) nanoparticles into optically active poly(ester-imide) (PEI), afforded an opportunity to prepare several novel PEI/TiO₂ bionanocomposites (BNC)s. To this point, firstly PEI was synthesized via direct polyesterification of chiral diacid monomer and an optically active phenolic diol using tosyl chloride/pyridine/N,N-dimethylformamide system as a condensing agent. Novel BNC polymers containing TiO₂ nanoparticles were synthesized through ultrasonic irradiation method. With the aim of γ-amidopropyl-triethoxylsilicane as a coupling agent, the surface of nanoscale TiO₂ was modified to decrease aggregation of nanoparticles in polymer matrix. The obtained PEI/TiO₂ BNCs were characterized with FT-IR, thermogravimetric analysis (TGA), scanning electron microscopy, X-ray diffraction, and transmission electron microscopy (TEM) techniques. Consequently, TEM image showed that the nanoparticles of smaller than 50 nm in diameter were uniformly dispersed in the polymer matrix. TGA data demonstrated that new synthesized PEI/TiO₂ BNCs are more thermally stable in compare to pure PEI.     

Preparation and swelling behavior of biodegradable hydrogels based on α,β‐poly(N‐2‐hydroxyethyl‐DL‐aspartamide)

Biodegradable polymers and the hydrogels have been increasingly applied in a variety of biomedical fields and pharmaceutics. α,β‐Poly(N‐2‐hydroxyethyl‐DL ‐aspartamide), PHEA, one of poly(amino acid)s with hydroxyethyl pendants, are known to be biodegradable and biocompatible, and has been studied as an useful biomaterial, especially for drug delivery, via appropriate structural modification. In this work, hydrogels based on PHEA were prepared by two‐step reaction, that is, the crosslinking of polysuccinimide, the precursor polymer, with oligomeric PEG or PEI‐diamines and the following nucleophilic ring‐opening reaction by ethanolamine. Soft hydrogels possessing varying degrees of gel strength could be prepared easily, depending on the amount of different crosslinking reagents. The swelling degrees, which were in the range of 10–40 g–water/dry gel, increased somewhat at higher temperature, and also at alkaline pH of aqueous solution. A typical hydrogel remained almost unchanged for 1 week, at 37°C in phosphate buffer of pH 7.4, and then seemed to degrade slowly as time. A porous scaffold could be fabricated by the freeze drying of water‐swollen gel. The PHEA‐based hydrogels have potential for useful biomaterial applications including current drug delivery system. © 2003 Wiley Periodicals, Inc. J Appl Polym Sci 90: 3741–3746, 2003     

Properties of poly(ethylene glycol)‐based bioelastomers

In this article, a series of poly(ether ester) bioelastomers, poly(PEG‐co‐CA)s (PECs), were synthesized by the melt polycondensation of citric acid (CA) and poly(ethylene glycol) (PEG) with molecular weights of 150, 200, 300, and 400. The measurements of the mechanical properties of the PEC series testified that these polymers were elastomers with a low hardness and high elongation, and the hydrolytic degradation of polymer films in a buffer of pH 7.4 at 37°C showed that the PECs had excellent degradability. The molecular weight of PEG had a strong influence on the degradation rates, water absorption rates, and mechanical performance of the PECs. The materials are expected to be useful for pressure hemostasis implementation in lacuna and other biomedical applications. © 2010 Wiley Periodicals, Inc. J Appl Polym Sci, 2010     

Synthesis and characterization of biodegradable block copolymers of poly(propylene fumarate‐co‐sebacate)‐co‐poly(ethylene glycol) and poly(ethylene fumarate‐co‐sebacate)‐co‐poly(ethylene glycol)

The synthesis of two low molecular weight linear unsaturated oligoester precursors, poly(propylene fumarate‐co‐sebacate) (PPFS) and poly(ethylene fumarate‐co‐sebacate) (PEFS), are described. PPFS, PEFS, and poly(ethylene glycol) are then used to prepare poly(propylene fumarate‐co‐sebacate)‐co‐poly(ethylene glycol) (PPFS‐co‐PEG) and poly(ethylene fumarate‐co‐sebacate)‐co‐poly(ethylene glycol) (PEFS‐co‐PEG) block copolymers. The products thus obtained are investigated in terms of the molecular weight, composition, structure, thermal properties, and solubility behavior. A number of design parameters including the molecular weights of PPFS, PEFS, and PEG, the reaction time in the polymer synthesis, and the weight ratio of PEG to PPFS or to PEFS are varied to assess their effects on the product yield and properties. The hydrolytic degradation of PPFS‐co‐PEG and PEFS‐co‐PEG in an isotonic buffer (pH 7.4, 37°C) is investigated, and it is found that the fumarate ester bond cleaves faster than does the sebacate ester bond. © 2004 Wiley Periodicals, Inc. J Appl Polym Sci 92: 295–300, 2004     

Formation of microcapsules of medicines by the rapid expansion of a supercritical solution with a nonsolvent

The rapid expansion from a supercritical solution with a nonsolvent (RESS‐N) was applied to the formation of polymeric microcapsules containing medicines such as p‐acetamidophenol, acetylsalicylic acid, 1,3‐dimethylxanthine, flavone, and 3‐hydroxyflavone. A suspension of medicine in carbon dioxide (CO₂) containing a cosolvent and dissolved polymer was sprayed through a nozzle to atmospheric pressure. The pre‐expansion pressure was 10–25 MPa, and the temperature was 308–333 K. The polymers were poly(L ‐lactic acid) (molecular weight = 5000), poly(ethylene glycol) (PEG; PEG4000, molecular weight = 3000; PEG6000, molecular weight = 7500; and PEG20000, molecular weight = 20,000), poly(methyl methacrylate) (molecular weight = 15,000), ethyl cellulose (molecular weight = 5000), and PEG–poly(propylene glycol)–PEG triblock copolymer (molecular weight = 13,000). The solubilities of the polymers as coating materials and these medicines as core substance were very low in CO₂. However, the solubilities of these polymers in CO₂ significantly increased with the addition of low molecular weight alcohols as cosolvents. After RESS‐N, polymeric microcapsules were formed according to the precipitation of the polymer caused by a decrease in the solvent power of CO₂. This method offered three advantages: (1) enough of the coating polymers, which were insoluble in pure CO₂, dissolved; (2) the microparticles of the medicine were encapsulated without adhesion between the particles because a nonsolvent was used as a cosolvent and the cosolvent remaining in the mixture was removed by the gasification of CO₂; and (3) the polymer‐coating thickness was controlled with changes in the feed composition of the polymer for drug delivery. © 2003 Wiley Periodicals, Inc. J Appl Polym Sci 89: 742–752, 2003     

Effect of molecular weight on spherulitic growth rate of poly(ϵ‐caprolactone) and poly(ϵ‐caprolactone)‐b‐poly(ethylene glycol)

The spherulitic growth rates of a series poly (?‐caprolactone) homopolymers and poly(?‐caprolactone)‐b‐ poly(ethylene glycol) (PCL‐b‐PEG) block copolymers with different molecular weights but narrow polydispersity were studied. The results show that for both PCL homopolymers and PCL‐b‐PEG block copolymers, the spherulitic growth rate first increases with molecular weight and reaches a maximum, then decreases as molecular weight increases. Crystallization temperature has greater influence on the spherulitic growth rate of polymers with higher molecular weight. Hoffman–Lauritzen theory was used to analyze spherulitic growth kinetics and the free energy of the folding surface (σ_e) was derived. It is found that the values of σ_e decrease with molecular weight at low molecular weight level and become constant for high molecular weight polymers. The chemically linked PEG block does not change the values of σ_e significantly. © 2007 Wiley Periodicals, Inc. J Appl Polym Sci 2007