表面活性劑在(zai)水中隨著濃度增大， 表面上聚集的(de)活性(xing)劑分(fen)子(zi)(zi)形(xing)成定向排(pai)列的(de)緊密單分(fen)子(zi)(zi)層(ceng)，多余的(de)分(fen)子(zi)(zi)在(zai)體相內部也三三兩兩的(de)以憎水基互相靠(kao)攏，聚集在(zai)一起形(xing)成膠(jiao)束，這開始形(xing)成膠(jiao)束的(de)低濃度稱為(wei)臨界(jie)膠(jiao)束濃度。? ?

這時(shi)溶液(ye)性質與理想性質發生偏離，在表面張力對(dui)濃(nong)度繪制的曲線上會(hui)出(chu)現(xian)轉折。繼續增加活(huo)性劑濃(nong)度，表面張力不(bu)再降低，而(er)體(ti)相中的膠束(shu)不(bu)斷增多(duo)、增大。? ?

表面活(huo)(huo)性(xing)(xing)劑在(zai)溶液中分散，當達到(dao)一(yi)定(ding)濃(nong)(nong)度(du)時(shi)，表面活(huo)(huo)性(xing)(xing)劑分子(zi)(zi)會從單體(ti)( 單個離子(zi)(zi)或(huo)分子(zi)(zi)) 締合(he)成為(wei)膠(jiao)態(tai)聚集(ji)物，形(xing)成膠(jiao)團(tuan)。溶液性(xing)(xing)質隨(sui)之發生突變，此時(shi)的濃(nong)(nong)度(du)，即(ji)形(xing)成膠(jiao)團(tuan)時(shi)的濃(nong)(nong)度(du)，稱為(wei)臨界膠(jiao)團(tuan)濃(nong)(nong)度(du)(critical?micelle?concentration，簡寫為(wei)CMC) ，表面活(huo)(huo)性(xing)(xing)劑形(xing)成膠(jiao)團(tuan)的過程稱為(wei)膠(jiao)團(tuan)化作用。? ?

表面活性(xing)劑(ji)分子締(di)合(he)形成膠束的低濃(nong)度。當(dang)其濃(nong)度高于CMC值時，表面活性(xing)劑(ji)的排(pai)列成球狀(zhuang)、棒狀(zhuang)、束狀(zhuang)、層狀(zhuang)/板狀(zhuang)等(deng)結構。 ???

增(zeng)(zeng)(zeng)溶(rong)(rong)(rong)體(ti)系為熱力學平衡體(ti)系；CMC 越(yue)低、締合數越(yue)大，增(zeng)(zeng)(zeng)溶(rong)(rong)(rong)量（MAC）就(jiu)越(yue)高；溫(wen)(wen) 度(du)對增(zeng)(zeng)(zeng)溶(rong)(rong)(rong)的(de)影響：溫(wen)(wen)度(du)影響膠束(shu)的(de)形成，影響增(zeng)(zeng)(zeng)溶(rong)(rong)(rong)質的(de)溶(rong)(rong)(rong)解(jie)，影響表面活性劑的(de)溶(rong)(rong)(rong)解(jie)度(du)?離子型表面活性劑的(de)溶(rong)(rong)(rong)解(jie)度(du)隨溫(wen)(wen)度(du)增(zeng)(zeng)(zeng)加而急劇增(zeng)(zeng)(zeng)大這一溫(wen)(wen)度(du)稱(cheng)為Krafft點，Krafft點越(yue)高，其臨界膠束(shu)濃度(du)越(yue)小。 ? 

對于聚(ju)氧(yang)乙烯型(xing)非(fei)離子表面活性劑，溫(wen)度(du)(du)升高到一定程度(du)(du)時，溶解(jie)度(du)(du)急劇下降并析出(chu)(chu)，溶液出(chu)(chu)現混濁，這一現象稱(cheng)為起(qi)曇(tan)，此(ci)溫(wen)度(du)(du)稱(cheng)為曇(tan)點。在(zai)聚(ju)氧(yang)乙烯鏈(lian)相同時，碳(tan)氫(qing)鏈(lian)越(yue)長，濁點越(yue)低(di)；在(zai)碳(tan)氫(qing)鏈(lian)相同時，聚(ju)氧(yang)乙烯鏈(lian)越(yue)長則濁點越(yue)高。 ???

非極性(xing)(xing)有(you)(you)機物如苯在水(shui)中(zhong)溶(rong)解(jie)(jie)度(du)很小,?加(jia)入油酸(suan)鈉等表面活性(xing)(xing)劑后,?苯在水(shui)中(zhong)的(de)(de)溶(rong)解(jie)(jie)度(du)大(da)大(da)增(zeng)(zeng)加(jia),?這稱為增(zeng)(zeng)溶(rong)作(zuo)用。 增(zeng)(zeng)溶(rong)作(zuo)用與普通(tong)的(de)(de)溶(rong)解(jie)(jie)概念是不同(tong)(tong)的(de)(de),?增(zeng)(zeng)溶(rong)的(de)(de)苯不是均勻分(fen)散在水(shui)中(zhong),?而是分(fen)散在油酸(suan)根分(fen)子形成的(de)(de)膠束中(zhong)。經(jing)X 射(she)線衍(yan)射(she)證實,?增(zeng)(zeng)溶(rong)后各種膠束都有(you)(you)不同(tong)(tong)程度(du)的(de)(de)增(zeng)(zeng)大(da),?而整個溶(rong)液的(de)(de)的(de)(de)依數(shu)性(xing)(xing)變化不大(da)。