Nā ʻano kūkulu o nā Cellulose Ethers

Nā ʻetera cellulosehe hui ia o nā polymers kūlohelohe i hoʻololi ʻia i loaʻa mai ka cellulose, ka biopolymer nui loa ma ka Honua. Ma ke ʻano he mau mea i loaʻa mai ka cellulose, mālama nā ethers cellulose i nā hiʻohiʻona kūkulu kumu o ka cellulose ʻoiai e hoʻokomo pū ana i nā hui ether e hoʻohuli nui i ko lākou solubility, rheological behavior, thermal stability, a me ka reactivity chemical. Hoʻohana nui ʻia kēia mau mea i nā ʻoihana mai nā lāʻau lapaʻau a me ka meaʻai a hiki i ke kūkulu ʻana a me ka mālama pilikino, ma muli o kā lākou hui kū hoʻokahi o nā waiwai.

1. Cellulose: Ke ʻAno o ka Iwi Kuamoʻo

He polysaccharide linear ka Cellulose i haku ʻia me nā ʻāpana β-D-glucose i hoʻopili ʻia e nā pilina β-1,4-glycosidic. Hoʻohuli ʻia kēlā me kēia ʻāpana glucose i 180° e pili ana i kona mau hoalauna, e hopena ana i kahi kaulahao i hoʻonohonoho pono ʻia a hoʻolōʻihi ʻia. Hoʻokumu kēia mau kaulahao i nā pilina hydrogen intermolecular ikaika, e hana ana i kahi ʻano paʻa a crystalline. Loaʻa i kēlā me kēia ʻāpana anhydroglucose (AGU) i loko o ka cellulose ʻekolu mau hui hydroxyl (–OH), aia ma nā kūlana C2, C3, a me C6. He pane nui kēia mau hui hydroxyl a lawelawe ma ke ʻano he mau wahi mua no ka hoʻololi kemika.

2. Ka Etherification o Cellulose

Hoʻopuka ʻia nā cellulose ethers ma ka hoʻopili ʻana i ka cellulose me nā alkylating agents i ke alo o kahi kumu ikaika, ʻo ia hoʻi ka sodium hydroxide. Hoʻololi kēia kaʻina hana i nā hui hydroxyl o ka cellulose me nā hui ether like ʻole e like me ka methyl (–CH₃), hydroxyethyl (–CH₂CH₂OH), a i ʻole carboxymethyl (–CH₂COOH). ʻO ke ʻano hana maʻamau e pili ana i ka hoʻoulu ʻana o nā cellulose hydroxyls e hana i nā ion alkoxide, a laila e hana me kahi etherifying agent.

ʻO ke ʻano o ka mea pani i hoʻokomo ʻia e hoʻoholo i ka papa o ka cellulose ether. Eia kekahi laʻana:

Methylcellulose (MC)– Hoʻololi ʻia me nā hui methyl.

ʻO ka Hydroxyethylcellulose (HEC)– Hoʻololi ʻia me nā hui hydroxyethyl.

ʻO Carboxymethylcellulose (CMC)– Hoʻololi ʻia me nā hui carboxymethyl.

ʻO ka Hydroxypropylcellulose (HPC)- Hoʻololi ʻia me nā hui hydroxypropyl.

ʻEtilselulosa (EC)– Hoʻololi ʻia me nā hui ethyl.

Hāʻawi kēlā me kēia o kēia mau mea i loaʻa mai i nā waiwai kikoʻī, e like me ka solubility i ka wai, ka hoʻokumu ʻia ʻana o ka ʻiliʻili, ka mānoanoa, a me ka thermal gelation, i hana ʻia no nā noi kikoʻī.

3. Kekelē o ka Hoʻololi (DS) a me ka Hoʻololi Molar (MS)

ʻO kekahi o nā ʻano hoʻonohonoho koʻikoʻi o nā ethers cellulose ʻo ia ke kekelē o ka pani ʻana (DS), e pili ana i ka helu awelika o nā hui hydroxyl ma kēlā me kēia ʻāpana glucose i pani ʻia e nā hui ether. No ka mea he ʻekolu mau hui hydroxyl no kēlā me kēia AGU, ʻo ka DS kiʻekiʻe loa he 3.

ʻO kekahi mau ethers cellulose, e like me ka hydroxyethylcellulose a i ʻole hydroxypropylmethylcellulose, e pili ana i nā kaulahao ʻaoʻao e hiki ke lawe i nā hui hydroxyl hou aʻe. I ia mau hihia, hoʻohana ʻia ka molar substitution (MS) e wehewehe i ka helu awelika o nā moles o nā hui substituent i hoʻopili ʻia no kēlā me kēia AGU. Hiki iā MS ke ʻoi aku ma mua o 3 no ka mea he helu ia no ka etherification hou aʻe ma nā kaulahao substituent.

Hoʻololi koʻikoʻi ka DS a me MS i ka solubility, viscosity, a me ke ʻano wela o nā cellulose ethers. Hoʻomaikaʻi ka DS kiʻekiʻe i ka solubility i ka wai a i ʻole nā ​​​​​​mea hoʻoheheʻe organik a hoʻololi i ke ʻano gelation. No ka laʻana, ʻaʻole hiki ke hoʻoheheʻe ʻia ka carboxymethylcellulose DS haʻahaʻa i ka wai, ʻoiai nā ʻano DS kiʻekiʻe e hoʻoheheʻe koke ʻia.

4. Nā ʻĀpana Amorphous vs. Crystalline

Hōʻike ka cellulose maoli i kahi ʻano semi-crystalline, i haku ʻia me nā ʻāpana crystalline i hoʻonohonoho pono ʻia i hoʻopili ʻia me nā ʻāpana amorphous i hoʻonohonoho ʻole ʻia. Hoʻopaʻa ʻia nā ʻāpana crystalline e ka hoʻopaʻa hydrogen nui a me nā pilina van der Waals, e kūʻē ana iā lākou i ka hoʻololi kemika.

ʻOi aku ka maʻalahi o nā hopena etherification ma nā wahi amorphous, kahi e maʻalahi ai ke komo ʻana i nā kaulahao cellulose. Ke holomua nei ka hoʻololi ʻana, ua hoʻopilikia ʻia nā wahi crystalline, e hoʻonui ana i ka ʻike amorphous a, no laila, ka solubility o ka cellulose ether i ka wai a i ʻole nā ​​​​​​mea hoʻoheheʻe. ʻO kēia hoʻololi ʻana mai ka crystalline a i ka amorphous structure kahi hoʻololi koʻikoʻi i ka hana ʻana o nā cellulose ethers.

5. Ka hoʻoheheʻe ʻia a me ka hydrophilicity

ʻO ka hoʻololi ʻana o ke ʻano o ka cellulose ma o ka etherification e hoʻololi i kona hydrophilicity. Ma muli o ke ʻano a me ka nui o nā hui substituent, hiki ke hoʻoheheʻe ʻia nā cellulose ethers i ka wai, nā mea hoʻoheheʻe organik, a i ʻole nā ​​​​mea ʻelua. No ka laʻana:

He wai hoʻoheheʻe ʻia ka Methylcellulose a hōʻike i ka gelation thermal.

ʻAʻole hoʻoheheʻe ʻia ka Ethylcellulose i ka wai akā hiki ke hoʻoheheʻe ʻia i loko o nā mea hoʻoheheʻe organik e like me ka ethanol a me toluene.

ʻO ka Hydroxyethylcellulose a me ka hydroxypropylcellulose he hydrophilic kiʻekiʻe a hoʻoheheʻe ʻia i ka wai.

ʻO ka hoʻonui ʻia ʻana o ka solubility o nā cellulose ethers e kū mai ana mai ka hoʻopilikia ʻana o ka pilina hydrogen intermolecular i loko o ka cellulose maoli a me ka hoʻolauna ʻana o nā hui hydrophilic ether, hiki ke hana i nā pilina hydrogen hou me nā mole wai.

6. Nā Waiwai Rheological a me ke Kaumaha Molekala

ʻAʻole wale nā ​​​​ʻano hoʻololi ma nā kaulahao cellulose e hoʻopilikia akā i ka viscosity a me ka rheology o nā hopena wai. ʻO nā cellulose ethers he mau polymers kaumaha molekala kiʻekiʻe, a hōʻike kā lākou mau hopena i ke ʻano pseudoplastic (shear-thinning), kahi mea makemake nui ʻia i nā noi e like me nā pena, nā mea hoʻomānoanoa meaʻai, a me nā ʻano lāʻau lapaʻau.

Hoʻonui ka viscosity me ke kaumaha molekala a me ke kekelē o ka polymerization akā ua hoʻopilikia ʻia hoʻi e DS a me MS. ʻOi aku ka maʻalahi o ke kaulahao o nā ethers cellulose i hoʻololi nui ʻia a hoʻemi ʻia nā pilina interchain, e hopena ana i nā viscosities haʻahaʻa ma ka like like o ka hoʻohālikelike ʻia me nā ʻano i hoʻololi ʻole ʻia.

7. Paʻa Wela a me Kemika

Hoʻonui ka Etherification i ke kūpaʻa wela a me ke kemika o ka cellulose. Hāʻawi nā hui ether i pani ʻia i ka pale steric e kūʻē i ka hydrolytic a me ka oxidative degradation. Eia nō naʻe, ʻokoʻa ke ʻano wela ma muli o ke ʻano o ka substituent:

Hōʻike ʻo Methylcellulose a me hydroxypropylmethylcellulose i ka gelation thermal, kahi hana hoʻohuli kahi e hōʻuluʻulu ai nā kaulahao polymer ma ka hoʻomehana ʻana a hana i kahi gel.

ʻAʻole e hoʻopili ʻia ka Ethylcellulose i ka wā e hoʻomehana ʻia ai akā mālama i ka kūpaʻa o ke kūkulu ʻana i loko o kahi pae mahana ākea.

Ua hoʻomaikaʻi ʻia ke kū'ē kemika i nā waikawa a me nā kumu i nā ethers cellulose, ʻoi aku hoʻi nā mea me nā waiwai DS kiʻekiʻe. Eia nō naʻe, ʻoi aku ka maʻalahi o ka Carboxymethylcellulose i ka pH ma muli o kāna mau hui carboxyl anionic.

8. ʻAno a me ka Hoʻonohonoho ʻana o nā Molekala

ʻOiai he polymer linear ka cellulose, ʻo ka hoʻokomo ʻana o nā hui ether bulky hiki ke hana i ka wili kaulahao a i ʻole ka lālā hapa, ma muli o ka nui a me ka hydrophilicity o nā substituents. Hoʻopili kēia mau hoʻololi kūkulu i ke ʻano o ka hopena a me nā hiki ke hana ʻoniʻoni o nā cellulose ethers. ʻO ka hoʻolaha spatial o nā substituents ma ke kaulahao polymer e pili pū ana i nā pilina intermolecular a me ka hoʻohālikelike me nā polymers a i ʻole nā ​​​​mea hoʻohui ʻē aʻe.

9. Nā Waiwai Hana i Loaʻa mai ke ʻAno Hana

ʻO nā ʻano hoʻonohonoho kūikawā o nā cellulose ethers e hoʻolilo iā lākou i mau mea hana maʻalahi. ʻO kekahi mau hiʻohiʻona koʻikoʻi:

Hoʻokumu ʻia ʻana o ke kiʻiʻoniʻoni: Ma muli o ko lākou kaumaha molekala a me nā pilina kaulahao, hana nā cellulose ethers i nā kiʻiʻoniʻoni mānoanoa a maʻalahi hoʻi i hoʻohana ʻia i nā uhi a me ka hoʻopili ʻana.

Hoʻokuʻu lāʻau lapaʻau i kāohi ʻia: Hoʻohana ʻia nā waiwai hana gel a me ka pehu ʻana o nā cellulose ethers i nā papa lāʻau lapaʻau no ka hoʻomau ʻana o ka lawe ʻana i ka lāʻau.

ʻO ka Emulsification a me ka hoʻokuʻu ʻana: ʻO ke kaulike hydrophilic-lipophilic i hāʻawi ʻia e nā substituents kikoʻī e hiki ai i nā cellulose ethers ke hoʻopaʻa i nā emulsions a me nā suspensions.

Hoʻopili a me ka nakinaki ʻana: ʻO ko lākou hiki ke hana i nā pilina hydrogen me nā mea ʻē aʻe e hoʻolilo i nā cellulose ethers i mea hoʻopaʻa maikaʻi loa i ke kūkulu ʻana, nā keramika, a me nā huahana pepa.

ʻO kanā ʻano hoʻonohonoho o nā ethers cellulose—i wehewehe ʻia e kā lākou mau ʻano etherification, ke kekelē o ka hoʻololi ʻana, ka hoʻonohonoho molekala, a me nā waiwai kino i hopena ʻia—he mea nui ia i kā lākou hana ma nā ʻano noi like ʻole. Ma o ka hoʻololi kemika i kāohi ʻia o ka cellulose maoli, hiki ke hoʻomaikaʻi i ka solubility, viscosity, thermal behavior, a me ka hoʻohālikelike ʻana me nā mea ʻē aʻe. Ke hoʻomau nei nā ʻoihana e ʻimi i nā koho hoʻomau a biodegradable i nā polymers synthetic, manaʻo ʻia e ulu ka pilina a me ke koi no nā cellulose ethers, e hoʻolilo ana i ka ʻike hohonu o kā lākou pilina hoʻonohonoho-hana i mea nui.