Present research is concerned with polymerizations of various monomers on the surface of different clays. The monomers used were methyl methacrylate, vinyl chloride, acrylonitrile and N, N-dimethylaminoethyl methacrylate. The clays investigated were halloysite, bentonite, diatomaceous earth. A talc sample was also investigated for comparison. The clay surfaces were activated by acid treatment (50% $H_2SO_4$) and drying at 120℃ under vacuum, and the samples were subjected to one of the following three polymerization processes; 1) direct single step polymerization in which activated clay was dispersed directly into a polymerization mixture with an initiator such as AIBN and benzoyl peroxide, 2) redox polymerization in which N,N-dimethyl toluidine (or aniline) was adsorbed on the clay prior to the polymerization of monomers with a peroxide, and 3) solution polymerization in which solvents such as benzene, n-hexane and n-heptane were used as diluents, otherwise same to the above procedures.
After polymerization the polymer coated samples were subjected to solvent extraction to remove the loose polymers on the clay surface and analyzed by I.R., thermal gravimetric analysis, furnace combustion, and X-ray.
In the present, research were made the following observations :
ⅰ) Acid treatment activates and acidifies clay surface such that it improves polymerization yield as well as the amount of tightly bound polymers.
ⅱ) In solution polymerization the rate of polymerization dropped generally. When benzoyl peroxide was used as an initiator the best rate was observed in benzene compared with n-hexane.
ⅲ) Vinyl chloride polymerization on clay surface was greatly enhanced by applying pressure to the system.
ⅳ) Redox polymerization with N,N-dimethylaniline or copolymerization with monomer N,N-dimethylaminoethyl methacrylate improved the polymer adhesion to the clay.
ⅴ) Polymer-coated clay containing around 8% of polymer did not sediment in water for prolonged time period. (one month).
ⅵ) Acrylonitrile failed to polymerize well on clay surface.
ⅶ) Talc was found to be more active in polymerization than clays. However the portion of bound polymer was small.
ⅷ) Extensive coloration of clay was observed when redox system was used: for instance, halloysite/N,N-dimethylaniline + BPO: bright green.
고령토에 개시제와 모노머를 흡착시켜 라디칼 중합하였다. 황산의 농도를 바꾸어 가며 고령토를 산처리하여 개시제의 흡착능력을 비교하였으며 산처리한 고령토는 산성도와 표면적이 증가하였다.
고령토 표면에서의 라디칼 중합에 사용된 개시제로는 2,2'-azobisisobutyronitrile (AIBN) 을 사용하거나 N,N-dimethylaniline(DMA) 또는 N,N-dimethyltoluidine (DMT) 을 개시 촉진제로 사용하고 benzoyl peroxide (BPO) 를 개시제로 사용했으며 모노머는 methyl methacrylate (MMA), vinyl chloride (VCM), acrylonitrile(AN) 을 사용하고 N,N-dimethylaminoethyl methacrylate(DMAEMA) 를 comonomer로 5V/V%넣어 고령토 표면 중합의 정도를 비교하였다.
고령토 표면에서의 MMA중합은 단단계로는 잘 중합되었으나 용액중합의 경우는 MMA의 농도와 용매의 종류에 따라 크게 폴리머의 수득률에 차이가 생겼으며, VCM중합은 단단계 중합을 하였으며 중합조건을 바꾸어 가며 중합한 결과에 의하면 중합수율을 높이기 위해서는 고령토를 산처리하여 활성화시켜야 하고 반응기에 압력을 가하면서 온도를 높여주어야 한다.
DMA 와 DMAEMA 를 사용하면 친수성인 고령토와 소수성인 폴리머 사이의 결합력이 크게 증가되었으며 고령토 무게의 8% 정도만 폴리머가 덮여져 있어도 완전히 물에 뜰 정도로 고령토가 소수성 표면을 갖게 되었다.
고령토 표면에서의 AN의 중합은 AN이 고령토 표면의 Lewis 산성에 의해 다른 모노머보다도 더 큰 중합금지작용을 받아 중합수율이 매우 적었다.
활석은 고령토보다 중합이 잘 일어났으며 규조토는 가장 중합이 잘 일어났으나 폴리머와의 결합력이 작아 용매에 대부분 추출되었다. 이와같은 점토들간의 비교실험 결과에 의하면 점토표면에서 비닐 모노머를 중합시킬때 Lewis 산성도가 커지는데 비례해서 중합속도가 느려지거나 억제되었다. 그외 미량 포함된 전이금속의 존재도 영향을 주는 것으로 추정된다.
