Preparation of multihollow P(St-MAA) particles by sequence soap-free/soap emulsion polymerization and followed by stepwise alkali/acid posttreatment

The effects of ionic emulsifier, sodium dodecylbenzene sulfate (SDBS), on the formation of the multihollow structures in sub-micron sized polymer particles produced by alkali/acid posttreatment were investigated. The original latex particles with narrow size distribution were synthesized by a new sequence emulsifier-free/emulsifier emulsion copolymerization of styrene (St) and methacrylic acid (MAA). Results indicated that the pore size decreased and the pore number increased with the increase of SDBS amount, and the morphology of the posttreated latex particles was also significantly influenced by the introducing time of SDBS in the preparation of the original latex particles, and a suitable introducing time was 3 h of polymerization. (c) 2007 Cheng You Kan. Published by Elsevier B.V. on behalf of Chinese Chemical Society. All rights reserved.

INFLUENCES OF ACID POST-TREATMENT ON THE MORPHOLOGY OF SOAP-FREE P(MMA-EA-MAA)PARTICLES PREPARED BY SEEDED EMULSION POLYMERIZATION

Soap-free poly（methyl methacrylate-ethyl acrylate-methacrylic acid） latex particles with narrow size distribution were synthesized by seeded emulsion polymerization, and the porous particles were created by a stepwise alkali/acid treatment method. Effects of acid treatment conditions on the particle morphology were investigated. Results show that one to three pores were formed inside most of particles after post-treatment. At pH 7.0, when the treatment temperature was lower than 70℃, the size of particles and the volume of pores remained almost unchanged, and these two values increased significantly when the temperature was higher than 70℃. Both the particle size and the pore volume decreased with the increase of initial pH value and treatment time in the acid treatment. As the pH was below 4.0 and the treatment time was longer than 180 min, the particles shrunk in size.

The Growth of Latex Particles during the VAc/BA Copolymerization

The semi-continuous seeded emulsion eopolymerization of vinyl acetate and butyl acrylate was carried out with hydroxyethyl cellulose as a colloid stabilizer. The morphology of the latex particle and the relationship between the reaction time and the average particle diameter and/or the conversion ratio during the polymerization were invstiguted. The experimental results shaw that the morphology of the latex particle possesses the stable sterie construction. In the seeded polymerizution, the average particle diameter of latex decreased while the conversion ratio increased. At the second term of the emulsion copolymerization （the growth stage of particle size）, the latex particle average diameter increased with copolymerization continuously, but the instantaneous conversation ratio was not large, so it was very necessaO to properly prolong the time during the holding temperature stage.

Influences of Electrolytes on the Soap-free Emulsion Copolymerization of St-MMA-AA

Monodisperse functional polymer microspheres with different particle size and with clean surface were prepared by batch soap-free emulsion polymerization of styrene, methyl methacrylate and acrylic acid in the presence of salts, and the influences of type and amount of electrolytes on polymerization process and particle morphology were investigated. Results showed that there was a critical concentration for different electrolyte to make polymerization process and the resultant emulsion stable, and the particle size increased with the increase of electrolyte concentration. The effect of metal ions was Ca^2＋〉〉K^＋〉Na^＋〉Li^＋, and the effect of haloids was Br〉Cl〉F. Keywords： Electrolyte, soap-free emulsion polymerization, polystyrene, latex particle morphology.

STUDY ON THE FORMATION MECHANISM OF MONODISPERSE PARTICLES IN THE EMULSIFIER-FREE EMULSION POLYMEAIZATION OF METHYL METHACRYLATE AND BUTYL ACRYLATE

The formation mechanism of monodisperse polymer latex particles in the emulsifier-free emulsion polymerizationof methyl methacrylate and butyl acrylate with potassium persulfate as initiator was investigated. A multi-step formationmechanism for the monodisperse polymer particles was proposed. The nucleation mechanism is considered to be thecoagulation of the precursor particles by homogeneous nucleation when the primary particles reach a critical size with highsurface charge density and sufficient stability. It had been proved by a special experiment that the early latex particles formedby the coagulation were stable. The primary particles grow by absorbing monomers and radicals in the polymerization systemand then become colloidally unstable again due to the understandable decrease of particle surface charge density, which leadsto the aggregation of the growing particles and the formation of larger latex pedicles therefrom. Aner the nucleation period,the preferential aggregation of the smaller particles in the propagation process leads to the change of the particles towards auniform size and narrower particle size distribution. The coexistence and competition of homogeneous nucleation,coagulation, propagation and aggregation result in the increase of the polydispersity index (U = D_(43)/D_(10)) in the first Stage,then its decrease in the later stage because of the competition of propagation and aggregation, and the gradual formation ofthe monodisperse particles.

EFFECT OF PARTICLE SIZE ON THE FILMING PROCESS OF POLYSTYRENE LATEX STUDIED BY AFM

The film formation process of micro-PS particles (diameter 742 nm) and nano-PS particles (diameter 29 nm) was studied by atomic force microscopy and differential scanning calorimetry. During a step heating process, the particles were annealed for 0.5 h at each selected temperature. It was found that the deformation and interdiffusion temperatures of the micro-PS particles are ca. 120-130degreesC and 140-150degreesC, that of the nano-PS particles are 90degreesC and 100-110degreesC respectively. The DSC traces of nano-PS particles showed that there was an exothermic peak near T-g after annealing for 0.5 h at the selected temperatures below 90degreesC; otherwise, the exothermic peak disappeared after annealing at 100degreesC or above. Compared with the micro-PS particles, the sintering process of nano-PS particles occurs at much lower temperature determined by the confined state of polymer chains with higher conformational energy in nano-particles, and completes in a much narrower temperature range driven mainly by the larger total surface energy.

Determination of Size Distribution of Nano-particles by Capillary Zone Electrophoresis

A new method was developed for the determination of the size distribution of nano-particles by capillary zone electrophoresis (CZE). Scattering effect of nanoparticles was studied . This method for the determination of size distribution was statistical.

DESIGN AND CONTROL OF SOAP-FREE HYDROPHILIC-HYDROPHOBIC CORE-SHELL LATEX PARTICLES WITH HIGH CARBOXYL CONTENT IN THE CORE OF THE PARTICLES

Soap-flee hydrophilic-hydrophobic core-shell latex particles with high carboxyl content in the core of the particles were synthesized via the seeded emulsion polymerization using methyl methacrylate （MMA）, butyl acrylate （BA）, methacrylic acid （MAA）, styrene （St） and ethylene glycol dimethacrylate （EGDMA） as monomers, and the influences of MMA content used in the core preparation on polymerization, particle size and morphology were investigated by transmission electron microscopy, dynamic light scattering and conductometric titration. The results showed that the seeded emulsion polymerization could be carried out smoothly using ＂starved monomer feeding process＂ when MAA content in the core preparation was equal to or less than 24 wt%, and the encapsulating efficiency of the hydrophilic P（MMA-BA-MAA- EGDMA） core with the hydrophobic PSt shell decreased with the increase in MAA content. When an interlayer of P（MMA- MAA-St） with moderate polarity was inserted between the P（MMA-BA-MAA-EGDMA） core and the PSt shell, well designed soap-free hydrophilic-hydrophobic core-shell latex particles with 24 wt% MAA content in the core preparation were obtained.

不同附聚法聚丁二烯胶乳对ABS性能的影响

采用高分子附聚法和醋酸附聚法获得了大粒径聚丁二烯胶乳(PBL),然后与丙烯腈(AN)和苯乙烯(St)发生乳液接枝聚合反应,制得了丙烯腈-丁二烯-苯乙烯共聚物(ABS)高胶粉。将ABS高胶粉与丙烯腈-苯乙烯共聚物(SAN)共混挤出,制得了ABS树脂。研究了2种附聚法对PBL的粒子形态、粒径大小、粒径分布指数以及ABS树脂性能的影响。结果表明:与醋酸附聚法PBL相比,高分子附聚法PBL的粒径分布指数更大,普遍大于0.10,粒径均一性更差,且存在团聚现象;高分子附聚法PBL接枝后出现黏结现象;由高分子附聚法PBL所得ABS样条断面无明显的“海-岛”结构,抗冲击性能普遍较差。

600 nm粒径聚丁二烯胶乳的制备

以丁二烯为单体制备了小粒径聚丁二烯(PB)胶乳,并且用丙烯酸丁酯(BA)和甲基丙烯酸(MAA)制备了附聚剂。通过高分子附聚法附聚小粒径PB胶乳制备了600 nm大粒径PB胶乳,考察了附聚剂用量、电解质用量、附聚时间、附聚温度、搅拌速度等因素对大粒径PB胶乳的影响。结果表明:小粒径PB胶乳最佳粒径为100 nm,附聚剂中MAA适宜用量为20%,电解质用量为0.2%,适宜附聚时间为1~3 h,温度对附聚胶乳粒径的大小影响较小。

探究羧基含量对丁腈胶乳性能的影响

丁腈胶乳中引入羧基会对胶乳性能产生明显影响。探究不同羧基含量对胶乳粘度、粒径、结合腈含量、门尼粘度和物理机械性能的影响。实验结果表明,粒径和结合腈含量与羧基含量无关,粘度受羧基含量影响呈指数变化,门尼粘度和物理机械性能与羧基含量呈线性相关。

PREPARATION OF MICRON-SIZED NONSPHERICAL POLYSTYRENE/POLY(STYRENE-co-ETHYLENEGLYCOL DIMETHACRYLATE) PARTICLES BY SEEDED SOAP-FREE EMULSION POLYMERIZATION

Micron-sized nonspherical polymer particles having different morphologies were synthesized by seeded soap-free emulsion polymerization of styrene （St） and ethyleneglycol dimethacrylate （EGDMA, used as a crosslinker） on spherical, linear polystyrene （PS） seed particles. The morphology of the resulting PS/poly（St-co-EGDMA） particles was dependent on the crosslinker concentration and polymerization temperature.

Effect of Polymerization Condition on Particle Size Distribution in St/BA/MAA Emulsion Polymerization Process

A series of St/BA/MAA emulsion polymerizations was carried out. By using PCS (photon correlation spectroscopy), the particle size distribution (PSD) of the whole St/BA/MAA emulsion polymerization process was gotten easily and quickly. The effect of polymerization condition on PSD in St/BA/MAA emulsion process was discussed.

不同稳定剂对天然胶乳稳定性的影响

低氨、无氨浓缩胶乳在乳胶制品加工应用过程中存在性能不足的问题,包括稳定性较差、硫化速度慢、湿凝胶强度低等,主要与稳定剂的使用有关。稳定剂对天然胶乳的性能影响很大,本研究选用氢氧化钾(KOH)、氨、十二烷基硫酸钠(SDS)和月桂酸钾4种稳定剂添加到天然胶乳中,研究不同稳定剂对鲜胶乳和超低氨浓缩胶乳稳定性的影响。结果表明:KOH能快速提升天然胶乳pH;维持鲜胶乳黏度稳定;提升鲜胶乳的机械稳定性(MST),尤其是当用量超过0.3%时作用更明显;但KOH会使浓缩胶乳黏度上升,导致浓缩胶乳增稠,对提升浓缩胶乳MST和氧化锌机械稳定性(ZST)作用不明显;KOH能显著提升浓缩胶乳的热稳定性以及橡胶粒子的粒径。氨用量较低时能快速提升天然胶乳的pH,但用量较高时提升作用下降;氨能稳定鲜胶乳的黏度,提升鲜胶乳MST,但当用量超过0.2%时提升作用不明显;同时,氨能维持浓缩胶乳的流动性,稳定黏度值;氨对提升浓缩胶乳的MST、ZST和热稳定性作用不明显;对胶乳橡胶粒子的粒径影响较小。SDS单独添加时会导致鲜胶乳增稠;但能维持浓缩胶乳流动性,抑制黏度升高;能缓慢提升浓缩胶乳的MST和ZST,提高橡胶粒子粒径,但对热稳定性提升作用不明显。月桂酸钾单独使用时同样会导致鲜胶乳增稠,同时也会导致浓缩胶乳缓慢增稠;但月桂酸钾能快速提升浓缩胶乳MST和ZST,同时月桂酸钾会导致浓缩胶乳热稳定性快速下降,对提高橡胶粒子粒径也有一定效果,但当用量超过0.3%时粒径降低。因此,在浓缩胶乳生产过程中需要控制稳定剂的种类和用量。

强割和乙烯利刺激对不同品系幼龄橡胶树排胶生理特性的影响

【目的】研究不同割胶方式下不同品系幼龄橡胶树的排胶生理特性,为阐述乳管排胶机制提供理论基础,也为天然橡胶生产中针对不同品系进行合理规划割胶提供参考依据。【方法】选取PR107、RY8-79、Tjir1和RY7-33-97共4个品系的6龄未开割橡胶树,在S/2 d/2(割线长度为1/2茎围,每2天割1刀)的强割和后续添加1%乙烯利刺激割胶方式下,对其橡胶粒子粒径以及干胶含量、排胶体积、排胶时间、排胶初速度、堵塞指数、硫醇含量等常规排胶生理参数进行分析,并比较不同割胶刀次对这些参数的影响。【结果】(1)不同品系胶乳橡胶粒子粒径具有明显差异,起始值最大的是RY8-79和PR107,RY7-33-97的胶乳粒径较小,Tjir1的胶乳粒径最小。强割后,随着割胶刀次增加,不同品系胶乳粒径普遍短暂上升后降低,其中RY8-79和Tjir1的胶乳粒径变化较大,PR107和RY7-33-97的胶乳粒径相对稳定,但均在强割8刀后胶乳粒径降至0.80μm以下,与最大胶乳粒径之间存在显著差异(P<0.05)。乙烯利刺激后,胶乳粒径维持在较小水平。(2)干胶含量起始值最高为RY7-33-97,其次为RY8-79和PR107,最差为Tjir1。在强割条件下,RY8-79和RY7-33-97干胶含量下降较快,PR107和Tjir1干胶含量下降相对缓慢;乙烯利处理后,PR107干胶含量仅略有下降;RY8-79、RY7-33-97和Tjir1干胶含量相对下调趋势略明显,尤其是RY7-33-97。(3)强割条件下,不同品系的排胶时间和排胶体积变化规律高度一致,RY8-79排胶总体积和时间明显高于PR107、RY7-33-97和Tjir1;乙烯利处理后所有品系的排胶时间和总体积显著提高(P<0.05),其中PR107和Tjir1这2个排胶少的品系受乙烯利刺激的影响更明显。(4)强割条件下RY8-79和RY7-33-97排胶初速度明显高于PR107和Tjir1,但乙烯利刺激显著降低所有品系的排胶初速度。(5)强割条件下不同品系堵塞指数差异较大,RY8-79最低,RY7-33-97最高,乙烯利刺激明显降低该指数。(6)强割条件下RY8-79硫醇含量最高,其次为RY7-33-97、PR107,Tjir1最低,乙烯利刺激后48 h 4个品系硫醇含量均表现出降低趋势。【结论】不同品系对强割和乙烯利刺激后的排胶反应不同。强割和过度乙烯利刺激均不利于橡胶粒子粒径、干胶含量等产排胶相关参数的恢复。橡胶粒子粒径和干胶含量相对其他参数受周边环境影响较小,可作为衡量排胶是否过度的参考指标。橡胶粒子粒径0.80μm是一个较有标志性的值,胶乳粒径降到该值之下,预示应降低割胶强度。自然条件下排胶量大的品系通常不耐强割和乙烯利刺激,RY8-79和RY7-33-97作为主栽品种应尽量避免割胶中施加乙烯利,而PR107可配合施用乙烯利刺激剂。利用幼龄树,结合强割和乙烯利刺激,可以作为育种早期快速筛选不同品系是否具有耐割和耐刺激的方法之一,也为不同品系割胶制度的制定提供依据。

单分散聚苯乙烯和聚(苯乙烯-co-苯乙烯磺酸钠)乳胶粒的制备及其喷墨流畅性

为探究颜料墨水中固体颗粒粒径与喷墨流畅性之间的关系,制备了不同粒径的单分散球形聚苯乙烯(PSt)和聚(苯乙烯-co-苯乙烯磺酸钠)(P(St-co-SS))乳胶粒,探究了乳胶粒大小与分散液储存稳定性和喷墨流畅性的关系,并结合有限元与密度泛函计算,从理论角度解释乳胶粒大小与电荷对其喷墨流畅性的影响。结果表明:通过控制引发剂、乳化剂或水溶性单体的加入量,成功制备不同粒径的单分散球形PSt和P(St-co-SS)乳胶粒;固含量为10%的PSt和P(St-co-SS)乳胶粒分散液在4~50℃温度范围内储存4个月后分散稳定性均大于96%;随着分散液中乳胶粒粒径的增大,分散液的抽滤流速逐渐降低,且相同粒径下P(St-co-SS)较PSt分散体系的抽滤流速更高;粒孔比的增大会导致分散液在孔道内的流动体积降低,最终造成滤孔的堵塞,而微粒上表面活性剂的脱吸附是造成相同粒径下PSt体系抽滤流畅性低于P(St-co-SS)体系的原因。

高分子附聚剂增大聚丁二烯胶乳粒径的研究

用丙烯酸正丁酯(BA)和甲基丙烯酸(MAA)合成了高分子附聚剂,并制备了大粒径聚丁二烯胶乳(PBL)。研究了PBL含量(在规定条件下烘干后剩余部分占总量的质量分数)、附聚剂用量和附聚剂中MAA含量对附聚效果的影响。结果表明:当PBL质量分数为30.0%、附聚剂质量分数为2.5%~3.0%、附聚剂中MAA质量分数为15.0%时,可制得粒径大于300 nm、粒径分布为单峰的稳定PBL。

Self-assembly of latex particles for colloidal crystals

Self-assembly of latex particles is of great importance for fabricating various functional colloidal crystals. In this paper, we review recent research on the self-assembly of latex particles for colloidal crystals, covering the assembly forces and various assembly approaches of latex particles, including self-assembly by gravity sedimentation, vertical deposition, physical confinement, electric field, and magnetic field. Furthermore, some simple methods for assembling latex particles such as spin coating, spray coating, and printing are also summarized.