纳米聚N-异丙基丙烯酰胺微凝胶的光引发聚合

选择具有温敏性的高分子单体N－异丙基丙烯酰胺（N－isopropylacrylamide，NIPAM）为主单体，N，N′－亚甲基双丙烯酰胺（methylenebisacrylamide，MBA）为交联剂，运用光引发无皂乳液聚合的方法合成出粒径小于100nm的高分子微凝胶，并研究了在改变体系组成和条件时微凝胶粒径的变化。结果显示，在乳化剂临界胶束浓度以下，随着乳化剂浓度的提高，微凝胶粒子的粒径不断关小且趋向稳定；相比于热引发，产生的微凝胶具有较高的单分散性而且粒径较小。     

Engineering oligo(ethylene glycol)-based thermosensitive microgels for drug delivery applications

Novel oligo(ethylene glycol)-based thermosensitive microgels with well engineered core-shell structures were developed for storage and delivery of chemotherapeutic agents. The core is consisted of hydrophobic poly[2-(2-methoxyethoxy)ethyl methacrylate], while the shell is consisted of hydrophilic copolymer of 2-(2-methoxyethoxy)ethyl methacrylate with oligo(ethylene glycol) methyl ether methacrylates. These core-shell microgels exhibit tunable volume phase transition temperature and excellent colloidal stability across the physiologically important temperature range. The thickness of the hydrophilic shell can control the collapsing degree (or mesh size) of the hydrophobic core network, which can be utilized to significantly increase the loading capacity of the model hydrophobic drugs dipyridamole by tailoring the shell thickness of microgels. While the microgels are nontoxic, the drug molecules released from the microgels remain active to kill the cancer cells. The presented results provide important guidelines for the rational design of core-shell structured polymeric microgels for drug uptake and release applications.     

Quantitative analysis of the cross-linked structure of microgels using fluorescent probes

Properties of polymeric microgels are influenced by the internal polymer cross-linked structure, but tools to quantitatively analyze this internal structure are limited. With the finding that polymer networks alter the diffusivity and subsequent excimer formation of pyrene, this study used the ratio between pyrene excimer and monomer emission to determine the number of cross-links (N) and average pore size (ξ) in poly(ethylene glycol) diacrylate (PEGDA) microgels. A calibration curve to relate pyrene emission to N and ξ in PEGDA hydrogels was prepared and used to calculate N and ξ in PEGDA microgels. The pyrene emission indicated that PEGDA microgels had a higher cross-linking density and a smaller average pore size when compared with bulk cross-linked hydrogels of the same PEGDA concentration. The analytical method demonstrated in this study may be useful for fine-tuning polymeric microgel properties for a broad array of applications.     

Thermo-sensitive poly(N-vinylcaprolactam-co-acetoacetoxyethyl methacrylate) microgels: 2. Incorporation of polypyrrole

In a previous paper [Polymer (2003) in press DOI: 10.1016/j.polymer.2003.09.037] polymeric temperature-sensitive microgels were prepared by surfactant-free emulsion co-polymerization of N-vinylcaprolactam (VCL) and acetoacetoxyethyl methacrylate (AAEM). In the present work, VCL/AAEM microgels were used as a template for oxidative polymerization of pyrrole (Py). It was found that pyrrole polymerization takes place directly in microgel structure leading to composite particles. Influence of microgel structure and amount of incorporated polypyrrole (PPy) on particle properties is discussed. Obtained stable composite microgels show similar thermal sensitivity as VCL/AAEM particles with fully reversible collapse-swelling properties.     

聚合物微球支载L-脯氨酸磺酰胺的合成

以L-羟脯氨酸为手性原料,经过O-烷基化、氨化、磺酰化,制备L-脯氨酸磺酰胺手性单体,在AIBN引发下,与苯乙烯和二乙烯基苯溶液聚合制备了聚苯乙烯微球支载的L-脯氨酸磺酰胺化合物,用IR,1H NMR,13C NMR及元素分析对其进行表征,其支载容量为0.70 mmol/g,总产率27.66%,所得结果与其结构相吻合。     

3D printing of living structural biocomposites

Nature fabricates organic/inorganic composites under benign conditions, yet, in many cases, their mechanical properties exceed those of the individual building components it is made from. The secret behind the evolutionary pivot is the unique ability of nature to control structure and local composition of its materials. This tight control is often achieved through compartmentalization of the reagents that can be locally released. Inspired by nature, we introduce an energy-efficient process that takes advantage of the compartmentalization to fabricate porous CaCO₃-based composites exclusively comprised of nature-derived materials whose compressive strength is similar to that of trabecular bones. The unique combination of nature-derived materials, 3D printability, and good mechanical properties is achieved through the formulation of these materials: We combine microgel-based granular inks that inherently can be 3D printed with the innate potential of engineered living materials to fabricate bacteria-induced biomineral composites. The resulting biomineral composites possess a porous trabecular structure that comprises up to 93 wt% CaCO₃ and thereby can withstand pressures up to 3.5 MPa. We envisage this system to have the potential to be used in art restoration, serve as artificial corals to help the regeneration of marine reefs, and, with additional work, might even allow the reparation of broken or partially disintegrated natural mineral-based materials such as certain parts of bones.     

无皂乳液聚合制备含氟温敏型微凝胶

在微波辐射下,采用无皂乳液聚合方法,制备了稳定的含氟N-异丙基丙烯酰胺(FA-NIPAAm)温度敏感型微凝胶乳液.利用FT-IR表征了微凝胶的化学组成;采用激光光散射粒度仪(PCS)研究了微凝胶粒径在不同温度的变化,测定了微凝胶的低临界溶解温度(LCST);用透射电子显微镜(TEM)观察了微凝胶的形貌;考察了微凝胶乳液...     

Enabling the measurement of particle sizes in stirred colloidal suspensions by embedding dynamic light scattering into an automated probe head

A novel probe head design is introduced, which enables in-line monitoring of particle sizes in undiluted stirred fluids using dynamic light scattering. The novel probe head separates a small sample volume of 0.65 ml from the bulk liquid by means of an impeller. In this sample volume, particle sizing is performed using a commercially available fiber-optical backscatter probe. While conventional light scattering measurements in stirred media fail due to the superposition of Brownian’ motion and forced convection, undistorted measurements are possible with the proposed probe head. One measurement takes approximately 30 s used for liquid exchange by rotation of the impeller and for collection of scattered light. The probe head is applied for in-line monitoring of the particle growth during microgel synthesis by precipitation polymerization in a one liter laboratory reactor. The in-line measurements are compared to off-line measurements and show a good agreement.     

Synthesis and kinetics of microgel in inverse emulsion polymerization of acrylamide

The kinetic behavior is studied in inverse emulsion polymerization of acrylamide. The polymerization rate in a micelle is proportional to the monomer concentration and the effective average radical concentration. When concentrations of monomer and radical are too low to proceed the polymerization only, some finite final conversion is obtained. The micelles of various sizes have different effective average radical concentrations at the same monomer concentration. Therefore, the polymerization rate and the final conversion are different for various sized micelles. The minimum amounts of emulsifier required to get stable state during reaction is 10 and 7 wt% (based on oil phase) in toluene and n-heptane systems, respectively. Phase inversion is observed with the increase of viscosity during polymerization. The final latex coagulates obviously in the toluene system even with 10 wt% of emulsifier, however, it can be improved more in the n-heptane system with 10 wt% of emulsifier. The crosslinking agent which copolymerizes with the monomer was supposed to remain in the interface of micelles. Such interfacial copolymerization not only hardens particles but improves the stability of the system also, therefore avoiding coagulation among particles. An increase in the content of crosslinking agent leads to a more uniform size of final particles. The microgel added in the alkyd resin decreases the drying time. The greater the amount of microgel added, the shorter the drying time.     

Online Particle Size Measurement in Microgel Particle Suspensions: Principles and Data Analysis

If a gelled system is subjected to shearing or the concentration of reactive components is low, microgel particles are formed. Since labile microgel particles with high water capacities can often be found in food systems, and as they are important for the textural properties, particle size measurement is relevant for fundamental research and control of industrial processes. A chord length measurement system was tested for online particle sizing.