Application of response surface methodology to evaluate the effect of dry‐spinning parameters on poly (ε‐caprolactone) fiber properties

Poly (ε‐caprolactone) fibers were prepared by dry‐spinning method. The effect of processing parameters on linear density, mechanical, and morphological properties of fibers was investigated using the response surface methodology (RSM). This method allowed evaluating a quantitative relationship between polymer concentrations, spinning speed, and draw ratio on the properties of the fibers. Polynomial regression model was fitted to the experimental data to generate predicted response. The results were subjected to analysis of variance to determine significant parameters. It was found that all three parameters had significant effect on linear density of fibers. Combined effect of concentration and spinning speed was observed in which the linear density of fiber was more sensitive to changes in the solution concentration at lower spinning speed. Polymer concentration had the largest influence on the mechanical properties of fibers. An average cross‐sectional radius of fibers was affected by concentration and draw ratio in opposite manner. Among all three parameters, only polymer concentration had significant effect on circularity of fiber cross sections. By applying the RSM, it was possible to obtain a mathematical model that can be used to better define processing parameters to fabricate dry‐spun PCL fiber in a more rational manner. © 2015 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2015 , 132, 42113.     

Effects of wide‐range γ‐irradiation doses on the structures and properties of 4,4′‐dicyclohexyl methane diisocyanate based poly(carbonate urethane)s

For medical applications, 4,4′‐dicyclohexyl methane diisocyanate (HMDI)‐based poly(carbonate urethane)s were synthesized from HMDI and 1,4‐butanediol as hard segments and poly(carbonate diol) (number‐average molecular weight = 2000 g/mol) as soft segments. The effects of wide‐range γ irradiation on the samples were examined through a series of analytical techniques. Scanning electron microscopy revealed that γ irradiation etched and roughened the surfaces of the irradiated samples. The gel content and crosslinking density measurements confirmed that crosslinking occurred along with degradation at all of the investigated irradiation doses and the degree of both crosslinking and degradation increased with increasing irradiation dose. Fourier transform infrared spectroscopy demonstrated that chain scission in the γ‐irradiated samples occurred at the carbonate and urethane bonds. The decreasing molecular weight and tensile strength indicated that the degradation increased with the γ‐irradiation dose. Differential scanning calorimetry and dynamic mechanical thermal analysis indicated that γ irradiation had no significant effect on the phase‐separation structures. There was a slight reduction in the contact angle. An evaluation of the cytotoxicity demonstrated the nontoxicity of the nonirradiated and irradiated polyurethanes. © 2014 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2014 , 131, 41049.     

Preparation and characterization of mPEG‐g‐α‐zein biohybrid micelles as a nano‐carrier

A new kind of block copolymer micelles methoxy polyethylene glycol (mPEG) grafted α‐zein protein (mPEG‐g‐α‐zein) was synthesized. The chemical composition of mPEG‐g‐α‐zein was identified with the help of FT‐IR and ¹H‐NMR. The biohybrid polymer can self‐assemble into spherical core–shell nanoparticles in aqueous solution. Scanning electron microscopy (SEM) and atomic force microscopy (AFM) were used to investigate the self‐assembled morphology of mPEG‐g‐α‐zein. Dynamic light scattering (DLS) results showed that the particle size of mPEG‐g‐α‐zein was about 90 nm. Moreover, the nanoparticles had a very low critical micelle concentration value with only 0.02 mg/mL. Then, the anticancer drug curcumin (CUR) was encapsulated into the biohybrid polymer micelles. The in vitro drug release profile showed a zero‐order release of CUR up to 12 h at 37°C. Cell viability studies revealed that the mPEG‐g‐α‐zein polymer exhibited low cytotoxicity for HepG2 cells (human hepatoma cells). Consequently, the mPEG‐g‐α‐zein micelles can be used as a potential nano‐carrier to encapsulate hydrophobic drugs and nutrients. © 2015 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2015 , 132, 42555.     

Design and in vivo assessment of polyester copolymers based on trimethylene carbonate and ε‐caprolactone

Poly(trimethylene carbonate‐co‐caprolactone) (PTCL) copolymers with various trimethylene carbonate ratios were synthesized by ring‐opening polymerization and were used to prepare implants for an in vivo experiment. Medical silicone rubber was used as the control. Implants were prepared by compression molding with a laboratory instrument. The properties of these copolymer implants were investigated. PTCL implants and silicone rubbers were implanted subcutaneously in the dorsal region of New Zealand white rabbits. The assessment was performed 1, 2, 3, 4, 5, 6, 7, and 8 months postoperatively by the determination of the weight loss, water uptake, thermal behavior, molecular weight of the explanted implants, and histological examination. During the 8‐month implantation, the value of maximum weight loss was found to be 25%. A continuous decrease in the molecular weight occurred. No remarkable tissue reactions were observed during degradation, and foreign‐body reactions were similar to those of silicone rubbers, which are commercially available materials. In this study, we aimed to indicate the likely clinical behavior but good biodegradable properties of PTCL copolymers compared to those of silicone rubber. This may open a new avenue of application for them in the drug industry. © 2015 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2015 , 132, 41815.     

Carboxymethylation of γ‐irradiated starch

Low viscosity carboxymethyl corn starch was prepared by the reaction of γ‐irradiated starch with monochloroacetic acid in the presence of alkali. It was found that irradiation dose influences the product viscosity remarkably. The viscosity decreases as the irradiation dose level increases; however, the viscosity increases with the increasing dose rate and the degree of substitution (DS). γ‐Irradiation can activate the starch to react with monochloroacetic acid, and the more of the irradiation dose, the higher of the DS and the reaction efficiency. The product has the character of low viscosity at high concentration, and the more of the irradiation dose, the more similar of the rheological behavior to a Newtonian liquid. © 2006 Wiley Periodicals, Inc. J Appl Polym Sci 101: 2210–2215, 2006     

A poly(γ‐glutamic acid)‐based hydrogel loaded with superoxide dismutase for wound healing

The purpose of this study was to develop a poly(γ‐glutamic acid) (γ‐PGA)‐based hydrogel loaded with superoxide dismutase (SOD) to accelerate wound healing. First, γ‐PGA was modified with taurine (γ‐PGAS), and then the SOD‐loaded γ‐PGAS/γ‐PGA hydrogel (SOD‐PGAS/PGA‐H) was prepared by cross‐linking of ethylene glycol diglycidyl ether. The swelling behavior and water vapor transmission rate revealed that PGAS/PGA‐H could create a moist environment for wound surface. In vitro kinetics of SOD release showed that SOD released from PGAS/PGA‐H maintained high activity and SOD‐PGAS/PGA‐H effectively scavenged the superoxide anion. The results of our fibroblast proliferation experiments showed that PGAS/PGA‐H had good cytocompatibility. The effects of SOD‐PGAS/PGA‐H on wound healing were examined in a Type I diabetic rat model with full‐thickness wounds. Twenty‐one days after grafted to wounds, SOD‐PGAS/PGA‐H exhibited a higher rate of wound healing than control group and showed increased collagen deposition and epithelialization. SOD‐PGAS/PGA‐H seems to promote better wound healing and thus might be a promising candidate for wound healing management. © 2015 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2015 , 132, 42033.     

Formulation of silver chloride/poly(3‐hydroxybutyrate‐co‐3‐hydroxyvalerate) (AgCl/PHBV) films for potential use in bone tissue engineering

Orthopedic implant failure due to bacterial infection has been a concern in bone tissue engineering. Here, we have formulated a composite made of biodegradable polymer, i.e., poly(3‐hydroxybutyrate‐co‐3‐hydroxyvalerate) (PHBV), and silver chloride. Ag⁺ ions released from the AgCl/PHBV film can promote an aseptic environment by promoting inhibition of bacterial growth while maintaining bone cell growth, depending on AgCl loading. The objective of this study is to formulate AgCl/PHBV film(s) of varying composition so as to evaluate the dependence of AgCl loading in the film on antimicrobial activity and cytotoxicity. The release kinetics of silver ions from AgCl/PHBV film in aqueous and Dulbecco's Modified Eagle Medium showed similarity in the initial burst of ions during the first day of desorption followed by a gradual release of ions over extended time period. The antibacterial efficacy of AgCl/PHBV film against Escherichia coli, Staphylococcus aureus, and Pseudomonas aeruginosa was evaluated by microbiological assay, while cytotoxicity of the film toward MC3T3‐E1 cells was determined by MTT assay. For all compositions studied, a clear zone of inhibition around AgCl/PHBV film was noticed on a modified Kirby‐Bauer disk diffusion assay. We established that MC3T3‐E1 cell attachment on AgCl/PHBV film is strongly related to loading of AgCl in the film. © 2017 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2017 , 134, 45162.     

Mechanistic and catalytic studies of β‐nitroalcohol crosslinking with polyamine

β‐Nitroalcohols (βNAs) are promising corneoscleral crosslinking agents for the treatment of diseases such as keratoconus and myopia. Although it is believed that formaldehyde is released from the crosslinking reactions of βNAs, the mechanism by which βNAs react with amine‐functionalized polymers has yet to be known. In this study, we present the reaction mechanism of the βNA crosslinking. Fourier transform infrared (FTIR) and nuclear magnetic resonance (NMR) data provide strong evidence that formaldehyde is released during the reaction. Catalytic studies show that sodium bicarbonate (NaHCO₃) and salmon testes DNA accelerate the reaction while hydroxynitrile lyase from Arabidopsis thaliana decelerates the crosslinking reaction. These results suggest that βNAs are potential self‐administered crosslinking agents for future clinical use. © 2012 Wiley Periodicals, Inc. J. Appl. Polym. Sci., 2013     

The use of poly (ε‐caprolactone) to enhance the mechanical strength of porous Si‐substituted carbonate apatite

Poly(ε‐caprolactone) (PCL)/silicon‐substituted carbonate apatite (Si‐CO3Ap) composite derived from the interconnected porous Si‐CO3Ap reinforced with molten PCL was prepared. PCL was used to improve the mechanical properties of a porous apatite by a simple polymer infiltration method, in which the molten PCL was deposited through the interconnected channel of porous Si‐CO3Ap. The PCL covered and penetrated into the pores of the Si‐CO3Ap to form an excellent physical interaction with Si‐CO3Ap leading to a significant increase in diametral tensile strength from 0.23 MPa to a maximum of 2.04 MPa. The Si‐CO3Ap/PCL composite has a porosity of about 50–60% and an interconnected porous structure, with pore sizes of 50–150 μm which are necessary for bone tissue formation. These results could pave the way for producing a porous, structured biocomposite which could be used for bone replacement. © 2013 Wiley Periodicals, Inc. J. Appl. Polym. Sci., 2013     

Fabrication and properties of surface‐modified β‐Si3N4 whiskers reinforced dental resin composites

In this article, three kinds of surface‐modified methods were used to treat β‐Si₃N₄ whiskers before being incorporated into Bis‐GMA/TEGDMA dental resin matrix in order to improve the whiskers' reinforcing effect. The experimental results showed that composites with directly heat‐treated and then silanized β‐Si₃N₄ whiskers had the best reinforcing effect. They had flexural strength of 160 ± 7.0 MPa (mean ± SD; n = 6), compressive strength of 371 ± 1.4 MPa (mean ± SD; n = 5) and HRA of 48.4 ± 0.5(mean ± SD; n = 5), respectively. In addition, water sorption and solubility test demonstrated that the composites were reliable to use as the dental restoration materials. Therefore, the directly heat‐treated and then silanized β‐Si₃N₄ whiskers (better than β‐Si₃N₄ whiskers mixed with SiO₂ nanoparticles or SiO₂ sols) were most suitable fillers to reinforce dental resin composites. © 2012 Wiley Periodicals, Inc. J. Appl. Polym. Sci., 2013     

Characterization of degradation of polypropylene nonwovens irradiated by γ‐ray

Polypropylene is a leading commercial, fiber‐forming polymer due to its low cost and potential for making high strength fibers. As the polymer of choice in the biomedical field, polypropylene contains only two elements, namely carbon and hydrogen. As a result, it is very hydrophobic and bio‐inert lacking biodegradability in the landfill. Meltblown and spunbond polypropylene nonwovens were exposed to γ‐radiation doses up to 25 kGy. The changes in morphology, chemical, thermal, and tensile properties were characterized by various analytical techniques. Following γ‐radiation, the FTIR spectrum illustrated an increase in carbonyl groups suggesting radio‐oxidation. Additionally, there was a decrease in thermal and tensile properties indicating deterioration of the polymer. © 2013 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2014 , 131, 39917.     

Effects of copolymer microstructure on the properties of electrospun poly(l‐lactide‐co‐ε‐caprolactone) absorbable nerve guide tubes

The main objective of this work has been to study the effects of copolymer microstructure, both chemical and physical, on the microporosity, in vitro hydrolytic degradability and biocompatibility of electrospun poly(l ‐lactide‐co‐ε‐caprolactone), PLC, copolymer tubes for potential use as absorbable nerve guides. PLC copolymers with L : C compositions of 50 : 50 and 67 : 33 mol % were synthesized via the ring‐opening copolymerization of l ‐lactide (L) and ε‐caprolactone (C) at 120°C for 72 h using stannous octoate (tin(II) 2‐ethylhexanoate) and n‐hexanol as the initiating system. Electrospinning was carried out from solution in a dichloromethane/dimethylformamide (7 : 3 v/v) mixed solvent at room temperature. The in vitro hydrolytic degradation of the electrospun PLC tubes was studied in phosphate buffer saline over a period of 36 weeks. The microporous tubes were found to be gradually degradable by a simple hydrolysis mechanism leading to random chain scission. At the end of the degradation period, the % weight retentions of the PLC 50 : 50 and 67 : 33 tubes were 15.6% and 70.2%, respectively. Pore stability during storage as well as cell attachment and proliferation of mouse fibroblast cells (L929) showed the greater potential of the PLC 67 : 33 tubes for use as temporary scaffolds in reconstructive nerve surgery. © 2013 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 130: 4357–4366, 2013     

Chitosan‐modified d‐α‐tocopheryl poly(ethylene glycol) 1000 succinate‐b‐poly(ε‐caprolactone‐ran‐glycolide) nanoparticles for the oral chemotherapy of bladder cancer

Oral chemotherapy is quickly emerging as an appealing option for cancer patients. It is less stressful because the patient has fewer hospital visits and can still maintain a close relationship with health care professionals. Three kinds of nanoparticles made from commercial poly(ε‐caprolactone) (PCL) and self‐synthesized d‐α‐tocopheryl poly(ethylene glycol) 1000 succinate ‐b‐poly(ε‐caprolactone‐ran‐glycolide) [TPGS‐b‐(PCL‐ran‐PGA)] diblock copolymer were prepared in this study for the oral delivery of antitumor agents, including chitosan‐modified PCL nanoparticles, nonmodified TPGS‐b‐(PCL‐ran‐PGA) nanoparticles, and chitosan‐modified TPGS‐b‐(PCL‐ran‐PGA) nanoparticles. First, the TPGS‐b‐(PCL‐ran‐PGA) diblock copolymer was synthesized and structurally characterized. Chitosan was adopted to extend the retention time at the cell surface and thus increase the chance of nanoparticle uptake by the gastrointestinal mucosa and improve the absorption of drugs after oral administration. The resulting TPGS‐b‐(PCL‐ran‐PGA) nanoparticles were found to be of spherical shape and around 200 nm in diameter with a narrow size distribution. The surface charge of the TPGS‐b‐(PCL‐ran‐PGA) nanoparticles could be reversed from anionic to cationic after surface modification. The chitosan‐modified TPGS‐b‐(PCL‐ran‐PGA) nanoparticles displayed a significantly higher level of cellular uptake compared with the chitosan‐modified PCL nanoparticles and nonmodified TPGS‐b‐(PCL‐ran‐PGA) nanoparticles. In vitro cell viability studies showed the advantages of the chitosan‐modified TPGS‐b‐(PCL‐ran‐PGA) nanoparticles over Taxol in terms of their cytotoxicity against human RT112 cells. In summary, the oral delivery of antitumor agents by chitosan‐modified TPGS‐b‐(PCL‐ran‐PGA) nanoparticles produced results that were promising for the treatment of patients with bladder cancer. © 2013 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 130: 2118–2126, 2013     

Hybrid biomimetic electrospun fibrous mats derived from poly(ε‐caprolactone) and silk fibroin protein for wound dressing application

To achieve excellent biofunctionality of Bombyx mori silk fibroin (SF), we explored a novel hybridization method to combine the unique properties of SF with poly(ε‐caprolactone) (PCL) electrospun fibers. The hybrid electrospun fibers demonstrate excellent hydrophilicity and biocompatibility that are important to tissue engineering applications. The biomimetic fibrous structure was fabricated by conventional electrospinning of PCL. The individual surfaces of PCL electrospun fibers were coated with silk fibroin protein using a lyophilization technique. The SF coating layers were durable which were further developed by surface modification with fibronectin to improve their biological function. The hybrid electrospun fibers show excellent support for normal human dermal fibroblast (NHDF) cells adhesion and proliferation than neat PCL fibers, while the surface‐modified hybrid electrospun fibers show significantly enhanced proliferation of NHDF cells on their surface. This study indicates the new opportunity of fabrication technique that can construct a biomimetic fibrous structure while the original function as a biomaterial remained existing. © 2014 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2015 , 132, 41653.     

p(AAm/TA)‐based IPN hydrogel films with antimicrobial and antioxidant properties for biomedical applications

Interpenetrating polymer networks (IPN), either semi‐IPN (s‐IPN) or full IPN, based on a natural polymer tannic acid (TA) and synthetic poly(acrylamide) (p(AAm)) were prepared by incorporation of TA during p(AAm) hydrogel film preparation with and without crosslinking of TA simultaneously. The synthesis of p(AAm/TA) s‐IPN and IPN hydrogels with different amounts of TA were prepared by concurrent use of redox polymerization and epoxy crosslinking. The p(AAm)‐based hydrogels were completely degraded at 37.5°C within 9 and 2 days at pHs 7.4 and 9, respectively. Biocompatibility of p(AAm), s‐IPN, and IPN were tested with WST assay and double staining, they had 75% cell viability up to almost 20 μg mL^?1 concentration against L929 fibroblast cell. Antioxidant properties of IPN and s‐IPN hydrogels were investigated with FC and ABTS^? methods. Antimicrobial properties of TA‐containing s‐IPN, and IPN hydrogels were determined against three common bacterial strains, Escherichia coli ATCC 8739, Staphylococcus aureus ATCC 6538, and Bacillus subtilis ATCC 6633, and it was found that p(AAm/TA)‐based s‐IPN and IPN hydrogels are effective antimicrobial and antioxidant materials. Moreover, almost up to day‐long linear TA release profiles were obtained from IPN and s‐IPN hydrogels in phosphate buffer solution at pH 7.4 at 37.5°C. © 2015 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2015 , 132, 41876.     

Conformational and thermal analyses of α‐methoxy‐poly(ethylene glycol)‐block‐poly[ϵ‐(benzyloxycarbonyl)‐l‐lysine] hybrid block copolymers

Hybrid block copolymers find applications in drug delivery, tissue engineering, biomimetics and bioimaging, amongst others, mainly due to their propensity to form phase‐separated microdomains as well as to the aggregation of their polypeptide segments. They not only enhance control over structure at the nanometre scale but also yield materials that can interface with various biosystems for different utilities. α‐Methoxy‐poly(ethylene glycol)‐block‐poly[?‐(benzyloxycarbonyl)‐l ‐lysine] hybrid block copolymers of varying degrees of polymerization, MPEG_n‐b‐PLL(Z)_m, were synthesized by N‐carboxyanhydride ring‐opening polymerization and characterized using infrared and NMR spectroscopy and gel permeation chromatography. Their secondary structures and bulk conformations were investigated using circular dichroism spectroscopy and wide‐angle X‐ray diffraction, respectively, whereas thermogravimetric analysis (TGA), derivative TGA and differential scanning calorimetry were employed for thermal analyses. The resulting block copolymers exhibited microphase separation and suppressed degrees of crystallinity with increasing l ‐lysine content and adopted α‐helix and β‐sheet secondary structures in aqueous milieu. The copolymers were also more thermally stable than their constituent homopolymers. Interestingly, the effects of the retention of the N^?‐benzyloxycarbonyl moiety on polymer properties proved considerable. The hybrid block copolymers herein afforded hierarchical structures of potential utility in the biomedical and pharmaceutical fields. © 2012 Society of Chemical Industry     

Surface‐modified pliable PDLLA/PCL/β‐TCP scaffolds as a promising delivery system for bone regeneration

Surface‐modified poly(d , l ‐lactide)/polycaprolactone/β‐tricalcium phosphate complex scaffold was fabricated in this study and we hypothesized that pliable and mechanical strong scaffold would be achieved by regulation of ternary compositions; while superficial modification strategy conduced to preserve and controlled‐release of bioactive growth factors. Properties of the composite scaffolds were systematically investigated, including mechanical properties, surface morphology, porosity, wettability, and releasing behavior. Moreover, the representative cytokine, recombinant human bone morphogenetic protein‐2 (rhBMP‐2), was loaded and implanted into muscular pouch of mouse to assess bone formation in vivo. Improved osteogenesis was achieved ascribed to both amplified β‐tricalcium phosphate (β‐TCP) content and retarded initial burst release. Particularly, scaffold doped with hydroxypropyl methylcellulose (HPMC) displayed optimal osteogenic capability. The results indicated that the PDLLA/PCL/β‐TCP complex scaffold along with HPMC‐coating and rhBMP‐2 loading was a promising candidate for bone regeneration. © 2014 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2014 , 131, 40951.     

Polymeric calcium phosphate cements incorporated with poly‐γ‐glutamic acid: Comparative study of poly‐γ‐glutamic acid and citric acid

Polymeric calcium phosphate cements (PCPC) derived from biodegradable poly‐γ‐glutamic acid (γ‐PGA) were prepared in an attempt to improve the mechanical strength of calcium phosphate cement (CPC). The characteristics of the PCPCs were compared with those of cement incorporated with citric acid. The diametral tensile and compressive strengths of the CPC incorporated with γ‐PGA were significantly higher than that of cement incorporated with citric acid at equivalent concentrations (P < 0.05). The maximal diametral tensile and compressive strengths of the CPC incubated for 1 week in physiological saline solution were approximately 18.0 and 50.0 MPa, respectively. However, the initial setting time of the PCPC was slower than that of CPC incorporated with citric acid. The formation of ionic complexes between calcium ions and γ‐PGA was observed using FTIR spectroscopy. Hydroxyapatite (HA) formation was retarded by γ‐PGA incorporation according to scanning electronic microscopy (SEM) and powder X‐ray diffraction (XRD) observations. © 2009 Wiley Periodicals, Inc. J Appl Polym Sci, 2009     

Evolution of the properties of a poly(l‐lactic acid) scaffold with double porosity during in vitro degradation in a phosphate‐buffered saline solution

A poly(l ‐lactic acid) scaffold prepared by a combination of freeze‐extraction and porogen‐leaching methods was submitted to static degradation in a phosphate‐buffered saline solution at pH 7.4 and 37°C for up to 12 months. After 6 months of degradation, the scaffold maintained its integrity, although noticeable changes in its permeability and pore size were recorded. After 12 months, scanning electron microscopy pictures showed that most of the trabeculae were broken, and the sample disaggregated under minimum loading. Neither weight loss nor crystallinity changes in the first heating calorimetric scan were observed during the degradation experiment. However, after 12 months, a rise in the crystallinity from 13 to 38% and a drop in the glass‐transition temperature from 58 to 54°C were measured in the second heating scan. The onset of thermal degradation moved from 300 to 210°C after 12 months. Although the elastic modulus suffered only a very slight reduction with degradation time, the aggregate modulus decreased 44% after 6 months. © 2014 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2014 , 131, 40956.     

Degradation and antioxidant activity of κ‐carrageenans

κ‐Carrageenan was degraded by an oxidative method involving hydrogen peroxide (H₂O₂). The molecular weight was measured by gel permeation chromatography. The effects of the concentration of H₂O₂ and initial κ‐carrageenan, pH value, and degradation time on the molecular weights of the degraded products were studied. The structural change of the degraded κ‐carrageenans was characterized by Fourier transform infrared spectroscopy and determination of the sulfate content. The antioxidant activity of the degraded κ‐carrageenans was evaluated as scavengers of superoxide anions and hydroxyl radicals by application of flow injection chemiluminescence technology. The values of the 50% inhibition concentration (IC₅₀) against the superoxide anion of degraded κ‐carrageenans labeled A, B, C, and D (with weight‐average molecular weights of 3250, 5820, 15,080, and 209,000, respectively) were 2.65, 3.22, 6.66, and 8.13 mg/mL, respectively. As for hydroxyl radical scavenging, the IC₅₀ values of κ‐carrageenans A, B, C, and D were 0.014, 0.049, 0.062, and 0.110 mg/mL, respectively. The results indicated that the κ‐carrageenans with lower molecular weights had better antioxidant activity. © 2010 Wiley Periodicals, Inc. J Appl Polym Sci, 2010