Preparation of poly(N‐ethyl methacrylamide) particles via an emulsion/precipitation process: The role of the crosslinker

Monodisperse, thermosensitive poly(N‐ethyl methacrylamide) microgel particles were prepared by the batch precipitation/emulsion polymerization of water‐soluble N‐ethyl methacrylamide and the hydrophobic crosslinker ethylene glycol dimethacrylate initiated by potassium persulfate. Particular attention was paid to the effect of the crosslinker agent on the polymerization process (kinetics, conversion, and water‐soluble oligomer content). Particles were characterized in terms of their size distribution and swelling capacity. A polymerization mechanism for the water‐soluble monomer and non‐water‐soluble crosslinker is proposed and discussed on the basis of a combination of both emulsion and precipitation polymerization processes. © 2002 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 40: 1808–1817, 2002     

Thermal and thermoxidative degradations of starch and thermosensitive starch-g-BAM copolymers

Summary Thermal degradation under N₂atmosphere and thermoxidative degradation under air atmosphere of increasingly grafting efficiency values (i.e. GE%=0.0 to 35.5) for starch and starch grafted with N-tert-butylacrylamide thermosensitive copolymers (starch-g-BAM) by Ozawa and Kissinger methods using thermogravimetric analysis (TG) and differential scanning calorimetry techniques (DSC) at 10, 30 and 50% mass losses respectively have been studied. Influence of physical inter and intra molecular interactions on grafting and consequently on activation energy of degradation (E_a,d) was investigated using Ozawa's method, whereas linear dependence of E_a,don GE% by scaling relations using Kissinger's method was determined. Furthermore, the thermoxidative degradation induces the possibility of molecular rearrangement, cyclization and partial crosslinking that is deduced from the activation energy of degradation (E_a,d) and residual mass of TG profile. Thermal stability of starch does not alter as a result of different grafting efficiency percentages.     

电刺激腹中隔区对IL-1_β作用下兔POAH温敏神经元放电特性的影响

目的 :进一步探讨中枢解热机理。方法 :采用微电极细胞外记录 ,观察在致热原IL - 1β作用下电刺激兔腹中隔区 (VSA)对视前区 -下丘脑前部 (POAH)温度敏感神经元放电特性的影响。结果 :(1)IL - 1β 使热敏神经元放电频率减少时 ,电刺激腹中隔区可明显降低POAH热敏神经元的温度敏感系数。 (2 )IL - 1β 使冷敏神经元放电频率增加时 ,电刺激腹中隔区可增加POAH冷敏神经元的温度敏感系数。结论 :作为负调节中枢的VSA可通过影响致热原作用下POAH区温敏神经元放电特性而解热     

Control of thermoresponsivity of biocompatible poly(trimethylene carbonate) with direct introduction of oligo(ethylene glycol) under various circumstances

Poly(trimethylene carbonate) (PTMC) is a well‐known biodegradable polymer with good biocompatible properties which make it suitable for biomedical applications. Poly(5‐[2‐{2‐(2‐methoxyethoxy)ethyoxy}‐ethoxymethyl]‐5‐methyl‐1,3‐dioxa‐2‐one) (PTMC‐MOE3OM) and copolymers, bearing oligo ethylene glycol (OEG) at the side chain of PTMC backbone, were selected to investigate the cloud point behavior by solvents such as PBS, water, 10% ethanol solution and various ionic strengths. A pH‐responsive copolymer, poly(TMCM‐MOE3OM‐co‐(5‐methyl‐5‐carboxylic‐1,3‐dioxane‐2‐one)) as carboxylic acid carbonate showed a decreased critical temperature at pH 2. Photo‐responsive copolymer, poly(TMCM‐MOE3OM‐co‐coumarin derivatives) bearing 1% and 10% of photo‐induced molecules (7‐[(5‐(5‐methyl‐1,3‐dioxa‐2‐one)methoxy)]‐methoxy coumarin (TMCM‐coumarin)) exhibited a low cloud point because of the hydrophobic moieties. Meanwhile, alternative coumarin polymer including 2% of 4‐methyl‐7‐[(5‐(5‐methyl‐1,3‐dioxa‐2‐one)methoxy)butoxy)]‐methoxy coumarin (TMCM‐4‐methyl‐coumarin) has been successfully synthesized and copolymerized as a novel molecule. The various combinations of monomers were studied and the significant properties were determined via external triggers after copolymerization. This study showed basically synthetic progress toward designs and trivial rationalization of thermoresponsive copolymers close to body temperature. At present, various pendant groups as side part affect to the lower critical solution temperature (LCST) and biodegradable polymer in order to utilize the actual external stimuli application. © 2017 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2017 , 55, 3466–3474     

Thermosensitive Gels for the Topical Administration of Diltiazem

In the present work, thermosensitive systems were prepared, characterized, and proposed for diltiazem administration in the topical treatment of anal fissures. Methylcellulose and PluronicF127 were used as gelling polymers. Some low-toxicity molecules, such as sodium glycocholate, citric acid, and lactic acid, were added to gel formulations as counterions to enhance diltiazem lipophilicity. The systems were characterized by sol-gel transition temperature, viscosity, and rheological studies. The resulting data allowed us to determine which systems presented sol-gel transition. A change from Newtonian to plastic behavior at sol-gel transition temperature was observed. An increase in diltiazem pig skin permeability and two-fold skin accumulation was observed in the presence of citric acid.     

阳离子型温敏水凝胶的溶胀性能及其对表面活性剂的吸附行为

阳离子单体;温敏凝胶;阳离子型温敏水凝胶的溶胀性能及其对表面活性剂的吸附行为     

Effect of synthesis method and buffer composition on the LCST of a smart copolymer of N‐isopropylacrylamide and acrylic acid

Responsive polymers have been the focus of many studies during the past decade because of their ability to change according to environmental stimuli. In this paper, we report on the development of a method to synthesize a pH/temperature‐sensitive linear copolymer, poly(N‐isopropylacrylamide‐ co‐acrylic acid)(poly(NIPAAm‐co‐AAc)), with a molecular weight of about 10⁶–10⁵ Da in water using azobisisobutyronitrile (AIBN) as the initiator. The effects of the following on the lower critical solution temperature (LCST) of the copolymer and homopolymer of NIPAAm were investigated: the type of buffer salts and pH changes of test solutions, molecular weight and concentration of homopolymer/copolymer solutions, and AAc monomer molar feed ratio (mol%). The effects of different synthesis methods on the molecular weight and on the AAc content were also evaluated. The mechanism of action in environments with different pH values is discussed. Copyright © 2007 John Wiley & Sons, Ltd.     

聚N,N-二乙基丙烯酰胺温敏水凝胶的药物释放研究

在合成聚Ｎ,Ｎ－二乙基丙烯酰胺温敏水凝胶的基础上研究了该水凝胶在ＬＣＳＴ附近对药物的释放（以氟哌酸为主）。温度与交联度的变化对药物的释放皆有明显的影响。通过对释放曲线进行计算机模拟得到释放液浓度的经验公式,并从理论上初步解释了公式中各参数的物理意义。作出了理论近似计算得到的表观扩散系数的变化曲线,其在ＬＣＳＴ附近各温度的变化趋势符合预测     

Synthesis and functionalities of poly(N-vinylalkylamide). V. Control of a lower critical solution temperature of poly(N-vinylalkylamide)

N-vinyl-n-butyramide (NVBA), N-vinylisovaleramide (NVIVA), and N-vinyl-n-valeramide (NVVA), which are N-vinylalkylamides with different alkyl groups were synthesized and their solution behavior in a polymeric form was examined. Copolymers of N-vinylisobutyramide (NVIBA) with N-vinylacetamide (NVA), NVIBA with NVVA, and NVVA with NVA were prepared by the solution polymerization to control the LCSTs. The resultant polyNVBA showed a lower critical solution temperature (LCST) sharply at 32°C, but polyN-vinylisovaleramide (polyNVIVA) and polyN-vinyl-n-valeramide(polyNVVA) that have n-butyl and isobutyl groups, respectively, on their side chains were insoluble even in cold water. The water solubility of the resulting polymers was found to vary, depending on the molecular shapes as well as the side chain length of the alkyl groups in question. The copolymers consisting of NVVA, NVIBA, and NVA in water showed LCSTs sharply between 10 and 90°C, depending on changes in their comonomer content. It was found that the changes in LCST that are caused by the incorporation of comonomers are due to changes in the overall hydrophilicity of the polymer. © 1997 John Wiley & Sons, Inc. J Polym Sci A: Polym Chem 35: 3087–3094, 1997